Abstract:
Devices and methods for use in laser-assisted surgery, particularly cataract surgery. Specifically, the use of an optical fiber with a proximal and distal end, wherein the distal end has a non-orthogonal angle with the diameter of the optical fiber, to create an off-axis steam bubble for cutting and removing tissue in an operative region. Where the optical fiber is bent, rotating the fiber creates a circular cutting path for the steam bubble, allowing access to tissues that may normally be blocked by obstructions and obstacles.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application 8 claims benefit of U.S. Provisional Application Ser. No. 61/865,454 (Attorney Docket No. 41663-710.101), filed Aug. 13, 2013, the entire contents of which is incorporated herein by reference. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The field of the present application pertains to medical devices. More particularly, the field of the invention pertains to an apparatus, system, and method for laser assisted cataract surgery. 
       BACKGROUND OF THE INVENTION 
       [0003]    A “cataract” is a clouding of the lens in the eye that affects vision. Most people develop cataracts due to aging. The condition is not uncommon; it is estimated more than half of all Americans will either have a cataract or have had cataract surgery by age 80. 
         [0004]      FIG. 1  is a diagram of the human eye, included for background. The major features of the eye  100  comprise the cornea  101 , the anterior chamber  102 , the iris  103 , the lens capsule  104 , the lens  105 , the vitreous  106 , the retina  107 , and the sclera  108 . The lens capsule  104  has an anterior surface  109  bordering the anterior chamber  102  and a posterior surface  110  bordering the vitreous  106 . Most relevant to cataracts, the lens  105  within the lens capsule  104  is comprised of a nucleus  111  and cortex  112 . 
         [0005]    As shown in  FIG. 1 , the lens  105  within the eye  100  lies behind the iris  103 . In principle, it focuses light onto the retina  107  at the back of the eye  100  where an image is recorded. The lens  105  also adjusts the focus of the eye  100 , allowing it to focus on objects both near and far. 
         [0006]    The lens  105  contains protein that is precisely arranged to keep the lens  105  clear and allow light to pass through it. As the eye ages, the protein in the lens  105  may clump together to form a “cataract”. Over time, the cataract may grow larger and obscure a larger portion of the lens  105 , making it harder for one to see. 
         [0007]    Age-related cataracts affect vision in two ways. The clumps of protein forming the cataract may reduce the sharpness of the image reaching the retina  107 . The clouding may become severe enough to cause blurred vision. The lens  105  may slowly change to a yellowish/brownish tint. As the lens  105  ages, objects that once appeared clear may gradually appear to have a brownish tint. While the amount of tinting may be small at first, increased tinting over time may make it more difficult to read and perform other routine activities. 
         [0008]    Surgery is currently the only real treatment for cataracts. Each year, ophthalmologists in the United States perform over three million cataract surgeries. The vast majority of cataracts are removed using a procedure called extracapsular cataract extraction (ECCE). ECCE traditionally comprises of several steps. Incisions must first be made to the cornea  101  in order to introduce surgical instruments into the anterior chamber  102 . Through the incisions in the cornea  101  and the space of the anterior chamber  102 , the surgeon may remove the anterior face of the lens capsule  109  in order to access the lens underneath  105 . This phase of the surgery, known as capsulorhexis, is often the most difficult procedure in ECCE. 
         [0009]    Having gained access to the lens through capsulorhexis, a small amount of fluid may be injected into the exposed lens capsule  104  to improve access and maneuverability of the lens  105 . This phase of the surgery is known as hydrodissection to the skilled artisan. 
         [0010]    After loosening the lens, it must be extracted. Traditionally, the lens is manually extracted through a large (usually 10-12 mm) incision made in the cornea  101  or sclera  108 . Modern ECCE is usually performed using a micro surgical technique called phacoemulsification, whereby the cataract is emulsified with an ultrasonic handpiece and then suctioned out of the eye through incisions in the cornea  101 . 
         [0011]    A phacoemulsification tool may be an ultrasonic handpiece with a titanium or steel needle. The tip of the needle may vibrate at an ultrasonic frequency to sculpt and emulsify the cataract while a pump aspirates particles through the tip. In some circumstances, a second fine steel instrument called a “chopper” may be used to access the cataract from a side port to help with “chopping” the nucleus  111  into smaller pieces. Once broken into numerous pieces, each piece of the cataract is emulsified and aspirated out of the eye  100  with suction. 
         [0012]    As the nucleus  111  often contains the hardest portion of the cataract, emulsification of the nucleus  111  makes it easier to aspirate the particles. In contrast, the softer outer material from the lens cortex  112  may be removed using only aspiration. After removing the lens material from the eye  100 , an intraocular lens implant (IOL) may be placed into the remaining lens capsule  104  to complete the procedure. 
         [0013]    One variation on phacoemulsification is sculpting and emulsifying the lens  105  using lasers rather than ultrasonic energy. In particular, femtosecond laser-based cataract surgery is rapidly emerging as a potential technology that allows for improved cornea incision formation and fragmentation of the cataract. 
         [0014]    Phacoemulsification and laser-based emulsification, however, still have their shortcomings. Phacoemulsification requires the use of tools that propagate ultrasound energy along the length of the tool, from a proximal transducer to a distal tip. The propagation leads to the transmission of ultrasound energy along the tool to other tissues proximal to the eye  100 . Ultrasound tools also generate more heat than would be desirable for a procedure in the eye  100 . In addition, the mechanical requirements of propagating the ultrasound wave along the length of the tool often make it rigid and difficult to steer around corners or bends. 
         [0015]    Laser-based tools have their own drawbacks. Presently, manually controlled lasers require careful, precise movement since they can easily generate unwanted heat in the eye  100 . Laser fibers in the tool are also fragile, and thus easily damaged when attempting to navigate tight corners. Both limitations increase surgery time and raise safety concerns. 
         [0016]    An alternative to conventional laser systems, femtosecond laser systems have their advantages and drawbacks as well. Femtosecond laser systems may be used to create entry sites through the cornea  101  and sclera  108  into the eye  100 , as well as to remove the anterior face of the capsule  104 . Femtosecond laser energy may be focused within the lens nucleus  111  itself, and used to “pre-chop” the lens nucleus  111  into a number of pieces that can then be easily removed with aspiration. Femtosecond lasers, however, can only fragment the central portion of the lens  105  because the iris  103  blocks the peripheral portion of the lens  105 . Thus, use of another emulsification technology—ultrasound or conventional laser—is still necessary to fracture and remove the peripheral portion of the cataract in lens  105 , extending total procedure time. Furthermore, femtosecond laser systems are also expensive and costly to operate and maintain. 
         [0017]    As an alternative to a purely laser-based emulsification, certain systems may use the lasers to generate steam bubbles to create shockwaves to break up the cataract material during emulsification. 
         [0018]      FIG. 2  is a diagram of a multimode optical fiber  200  with a flat tip at the distal end  201 , included for illustration purposes. At the output of the distal end  201 , all laser energy originating from laser source  203 , and carried through optical fiber  200 , is absorbed at the surface of fiber  200 . If the laser energy is high enough, the surrounding water may vaporize and form a steam bubble  202 . If the laser continues to output energy, the steam bubble  202  may grow into a cylindrical shape. A cylindrically-shaped steam bubble only occurs when the absorption depth in the water is relatively short; light energy with a wavelength near 3 μm can produce a cylindrically shaped steam bubble while light energy near 2 μm does not. The cylindrically-shaped steam bubble  202  produces a mechanical action that can cut or disrupt tissue. 
         [0019]      FIG. 3  is a diagram of a multimode optical fiber  300  with a tapered (cone shaped) tip at the distal end  301 , included for illustration purposes. At the output of the distal end  301  of optical fiber  300 , all the laser energy may be absorbed at the surface of the cone shaped fiber. If the laser energy is high enough, the water vaporizes and forms steam bubble  302 . If the laser continues to output energy, then the steam bubble can grow into a spherically-shaped steam bubble. The dynamics of steam bubble generation can be found in “Effect of microsecond pulse length and tip shape on explosive bubble formation of 2.78 μm Er,Cr;YSGG and 2.94 μm Er:YAG laser”, Paper 8221-12, Proceedings of SPIE, Volume 8221 (Monday 23 Jan. 2013). 
         [0020]    In both  FIGS. 2 and 3 , the steam bubbles generated by the optical fibers are collinear with the optical fiber. Being collinear, the orientation of the steam bubbles relative to the optical fibers create problems in certain applications. For example, during capsulorhexis, where the anterior portion of the lens capsule is removed, the orientation of the steam bubble presents a challenge because the tools are oriented at a steep angle to the lens capsule through incisions at the edge of the cornea. 
         [0021]    Therefore, it would be beneficial to have a new method, apparatus, and system for using steam bubbles that are not collinear with the neutral axis of the optical fiber. 
       SUMMARY OF THE INVENTION 
       [0022]    In general, the present invention provides a device and method for laser assisted cataract surgery using laser energy emitted by optical fibers to create steam bubbles. In one aspect, the present invention provides for a surgical device comprising an optical fiber having a proximal end and distal end, wherein the optical fiber is configured to generate a steam bubble from light energy conveyed out the distal end of the fiber, the proximal end is operatively connected to a light source, and the distal end comprises a tip with a non-orthogonal tilted edge across the diameter of the fiber. 
         [0023]    A related device further comprises a tube that encloses the optical fiber. In some embodiments, the tube is pre-bent at a predetermined angle. In some embodiments, an angle of the tilted edge exceeds 45 degrees. In some embodiments, an angle of the tilted edge does not exceed 45 degrees. In some embodiments, the angle of the tilted edge exceeds 7 degrees but not 45 degrees. In some embodiments, the optical fiber is further configured to generate a second steam bubble from the application of laser energy. 
         [0024]    In another aspect, the present invention provides for a method that comprises transmitting light energy through an optical fiber, generating a steam bubble; and directing the steam bubble to an operative region of a patient, wherein the optical fiber has a proximal end and a distal end, the optical fiber being configured to generate the steam bubble from light energy conveyed out the distal end of the fiber, the proximal end being operatively connected to a light source, and the distal end comprising a tip with a non-orthogonal tilted edge across the diameter of the fiber. 
         [0025]    In related embodiments, the optical fiber is enclosed within a tube. In some embodiments, the tube is pre-bent at a predetermined angle. In some embodiments, the method further comprises axially rotating the tube to generate a circular cutting path for the steam bubble. In some embodiments, axially rotating the optical fiber to generate a circular cutting path for the steam bubble. In some embodiments, an angle of the tilted edge exceeds 45 degrees. In some embodiments, an angle of the tilted edge does not exceed 45 degrees. In some embodiments, the angle of the tilted edge exceeds 7 degrees but not 45 degrees. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0026]    The invention will be described, by way of example, and with reference to the accompanying diagrammatic drawings, in which: 
           [0027]      FIG. 1  illustrates the portions of the human eye, included for background; 
           [0028]      FIG. 2  illustrates a multimode optical fiber with a flat tip at the distal end, included for illustration purposes; 
           [0029]      FIG. 3  illustrates a multimode optical fiber with a tapered (cone shaped) tip at the distal end, included for illustration purposes; 
           [0030]      FIGS. 4A-4B  illustrate an optical fiber coupled to a laser source consistent with the prior art, included for explanative purposes; 
           [0031]      FIGS. 5A-5B  illustrate an optical fiber coupled to a laser source in accordance with an embodiment of the present invention; 
           [0032]      FIGS. 6A-6B  illustrate an optical fiber coupled to a laser source where a steam bubble may be deflected from the axis of the fiber by incorporating a fiber with tilted end and a laser source with high water absorption, in accordance with an embodiment of the present invention; 
           [0033]      FIGS. 7A-7B  illustrate an optical fiber coupled to a laser source where a steam bubble may be deflected from the axis of the fiber by incorporating a fiber with a tilted end at 35 degrees, in accordance with an embodiment of the present invention; 
           [0034]      FIGS. 8A-8B  illustrate an optical fiber with a tip with a tilt angle of 45 degrees, in accordance with an embodiment of the present invention; 
           [0035]      FIGS. 9A-9B  illustrate an optical fiber with a tip with a tilt angle of 50 degrees, in accordance with an embodiment of the present invention; 
           [0036]      FIGS. 10A-10B  illustrate an embodiment of the present invention where the steam bubble is deflected from the axis of the fiber by incorporating a laser source with high water absorption, a bent optical fiber, and a tilted tip; 
           [0037]      FIGS. 11A-11B  illustrate an embodiment of the present invention where the steam bubble is deflected at an angle of 35 degrees from the axis of the fiber by incorporating a laser source with high water absorption, a bent optical fiber, and a tilted tip; 
           [0038]      FIGS. 12A-12B  illustrate an embodiment of the present invention where the steam bubble is deflected from the axis of the fiber by incorporating a laser source with high water absorption, a bent optical fiber, and a tilted end at the fiber; and 
           [0039]      FIGS. 13A-13B  illustrate an embodiment of the present invention where the steam bubble only exits from the side from a bent optical fiber with a tilted end at the fiber. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0040]    Although certain preferred embodiments and examples are disclosed below, inventive subject matter extends beyond the specifically disclosed embodiments to other alternative embodiments and/or uses, and to modifications and equivalents thereof. Thus, the scope of the claims appended hereto is not limited by any of the particular embodiments described below. For example, in any method or process disclosed herein, the acts or operations of the method or process may be performed in any suitable sequence and are not necessarily limited to any particular disclosed sequence. Various operations may be described as multiple discrete operations in turn, in a manner that may be helpful in understanding certain embodiments; however, the order of description should not be construed to imply that these operations are order dependent. Additionally, the structures, systems, and/or devices described herein may be embodied as integrated components or as separate components. 
         [0041]    As is known in the art, the conveyance of light energy at an interface of two materials is affected by the angle of incidence of the light energy, the index of refraction of the two substances, and the critical angle of the interface. When light is travelling from a high index of refraction material to a low index of refraction material and the angle of incidence is below the critical angle, the light largely passes from the high index of refraction to a low index of refraction material. When light is travelling from a high index of refraction material to a low index of refraction material and the angle of incidence is above the critical angle, the light reflects off the interface. If some of the light is greater than the critical angle, the light will exit the fiber from the side of the fiber. If all of the light in the fiber hits the titled end at greater than the critical angle, then all of the light will exit the side of the fiber. 
         [0042]    Higher index materials have correspondingly smaller critical angles. For example, for light coming from fused silica into air, the critical angle is 44.6 degrees. In contrast, the critical angle in water is lower. 
         [0043]      FIG. 4  illustrates an optical fiber  402  coupled to a laser source  401  consistent with the prior art, included for explanative purposes. As shown in  FIG. 4A  specifically, the conveyance of laser energy into and out of the optical fiber  402  contemplates two acceptance angles: (a) the angle required for light traveling down a multimode optical fiber to remain in the fiber, and (b) the angle of the laser energy exiting the end of the fiber. Thus, laser energy traveling at angles greater than the fiber&#39;s acceptance angle  404  exits the fiber  402  prior to reaching the distal end  403 . When the laser energy exits the optical fiber  402 , the acceptance angle is represented by  405 . 
         [0044]      FIG. 4B  illustrates the distal end  403  of optical fiber  402  consistent with the prior art, included for explanation purposes. As shown in  FIG. 4B , the tip of the distal end  403  is formed by an orthogonal cut across the diameter of the optical fiber  402 . The cut forms an approximately a right angle, i.e., ninety degrees, with the length of the optical fiber  402 . In other words, the plane formed at the tip of distal end  403  is approximately orthogonal to the longitudinal axis of the optical fiber  402 . 
         [0045]    In some applications including the cutting of membranes, it is desirable to have the steam bubble perpendicular to the surface of the membrane. Thus, in some embodiments, the ability to add steam bubble deflection to the fiber can allow for sharper bends of the steam bubble relative to the membrane surface since fibers have a finite bending radius. 
         [0046]      FIG. 5  is a diagram of an optical fiber coupled to a laser source, in accordance with an embodiment of the present invention. Similar to  FIG. 4 , laser source  501  emits laser (light) energy into optical fiber  502  for transmission into the operative region. Being an optical fiber, the conveyance of laser energy into and out of the optical fiber  502  contemplates two acceptance angles: (i) the angle required for light traveling down a multimode optical fiber to remain in the fiber ( 504 ), and (ii) the angle of the laser energy exiting the end of the fiber ( 505 ). 
         [0047]    In contrast to  FIG. 4 ,  FIG. 5  specifically shows the effect of having a tilt angle  506  at the tip of the distal end  503  of optical fiber  502 . The angle of refraction  508  of the interface may be computed using Snells&#39; law and the index of refraction of the two medium. The effect of the tilted distal end  503  and the angle of refraction  508  produce an angle of deflection  509  from the axis of the optical fiber  502 . The light will exit from the tilted end of the fiber provided that the sum of the tilt angle  507  and acceptance angle  505  do not exceed the critical angle  510 . 
         [0048]      FIG. 5B  illustrates the distal end  503  of optical fiber  502 . As shown in  FIG. 5B , the tip of the distal end  503  is formed by a non-orthogonal cut across the diameter of the optical fiber  502 . The angle of the cut forms a non-right angle  510  with the length of the optical fiber. The adjacent angle  511  is identical to tilt angle  507  from  FIG. 5A  due to the rules of Euclidean geometry. 
         [0049]    The preferred embodiments generally use laser light with a short absorption depth in water, i.e., an absorption depth less than 20 μm, which requires a corresponding absorption coefficient greater than 500 cm −1 . Accordingly, the preferred embodiments make use of light energy with either (i) a wavelength shorter than 200 nm or (ii) a wavelength longer than 2.8 μm. Among the options with wavelengths longer than 2.8 μm, light with wavelengths of 3 μm, 4.5 μm, 6 μm and 10 μm may be especially effective in certain embodiments. In particular, light with a wavelength of 3 μm may be advantageous because its absorption depth is very short and appropriate optical fibers are inexpensive. In contrast, optical fibers capable of conveying light energy of 4.5 μm, 6 μm, and 10 μm wavelength are more costly. 
         [0050]    The preferred embodiments also make use of pulsed light energy. In some embodiments, the pulse width may be as long as 500 μs. Enhanced performance has been observed in embodiments that make use of pulse widths of 80 μs in length and shorter. Some embodiments make use of light energy with a pulse width of 60 μs. 
         [0051]      FIG. 6  is a diagram of an optical fiber coupled to a laser source where a steam bubble may be deflected from the axis of the fiber by incorporating a fiber with tilted end and a laser source with high water absorption, in accordance with an embodiment of the present invention. The embodiment may be used to facilitate cataract surgery or any surgical application that involves cutting tissue. In some embodiments, the formation and collapse of the steam bubble may generate a directional shock wave. 
         [0052]    The advantages of having a deflected steam bubble include (i) being able to reach locations that the tip of the optical fiber cannot reach, (ii) being able to deflect by rotation the fiber, (iii) being able to use the defection angle to add to mechanical bends of the optical fiber, and (iv) improving the surgeon&#39;s line of sight of the operative region and cutting process. 
         [0053]    In  FIG. 6A , optical fiber  601  conveys laser energy from laser source  602  to the tilted tip  603  at the distal end of the optical fiber  601 . Tilted tip  603  is shaped to tilt angle  604 . In  FIG. 6A , tilt angle  604  is set to 20 degrees. Laser energy conveyed down the optical fiber  601  from the laser source  602  generates steam bubble  605 . Steam bubble  605  is off-angle from the neutral axis of optical fiber  601 , directed at a deflection angle  606 . The combination of the tilted distal end  603  and the angle of refraction  607  produce the angle of deflection  606  from the axis of the optical fiber  601 . 
         [0054]    In  FIG. 6B , optical fiber  601  may be subject to axial rotation  608  to form circular cutting path  609  with the deflected steam bubble  605 . The circular cutting path  609  has the advantage of cutting holes with a larger diameter than fiber  601  itself. 
         [0055]      FIG. 7  is a diagram of an optical fiber coupled to a laser source where a steam bubble may be deflected from the axis of the fiber by incorporating a fiber with a tilted end at 35 degrees, in accordance with an embodiment of the present invention. Similar to  FIG. 6A , optical fiber  701  conveys laser energy from laser source  702  to tilted tip  703  at the distal end of optical fiber  701 . Tilted tip  703  is shaped to a 35 degree tilt angle  704 . Laser energy conveyed down optical fiber  701  from laser source  702  generates steam bubble  705 . The effect of tilted distal end  703  and angle of refraction  707  produce an angle of deflection  706  from the axis of optical fiber  701 . 
         [0056]    With a tilt angle  704  of 35 degrees, the tip of steam bubble  705  extends out well beyond the diameter of the fiber  701 . The deflection angle  706  allows the surgeon to cut the surface of the lens capsule while also keeping the fiber  701  parallel to the surface of the lens capsule, improving visibility of the operative region. This helps a surgeon see the location of the fiber tip  703  while cutting material below the fiber tip  703 . 
         [0057]    In  FIG. 7B , optical fiber  701  may be subject to axial rotation  708  to form circular cutting path  709  using deflected steam bubble  705 . As discussed earlier, the circular cutting path  709  has the advantage of cutting holes in the material with a larger diameter than the fiber  701  itself. Specifically, steam bubble  705  has a larger 35 degree tilt at its tip  703  that creates a larger circular cutting path  709  from the rotation of the optical fiber  701 . 
         [0058]      FIG. 8  is a diagram of an optical fiber  801  with a tip  802  with a tilt angle of 45 degrees, in accordance with an embodiment of the present invention. In practice, some light exits the tilted tip  802  and some light exits the side of fiber  801  because the critical angle of fused silica is 44.6 degrees in air and slightly lower in water. The light in fiber  801  that is below the critical angle and is refracted through the tilted surface and the laser light forms a steam bubble  803  at tilted tip  802 . The light in the fiber  801  that is above the critical angle is reflected off of the surface of tilted tip  802  and exits the side of the fiber  801 . This reflected laser energy forms a steam bubble  804  directed out the side of the fiber  801 . Thus steam bubbles  803 ,  804  are formed, both of which may be used to cut in two locations at once. By carefully selecting the angle of the tilted tip  802 , the relative size and power of the steam bubbles  803 ,  804  can be controlled. In some embodiments, steam bubbles  803  and  804  may merge due to their close proximity to each other. 
         [0059]      FIG. 8B  is a diagram of optical fiber  801  with fiber rotation  805 , in accordance with an embodiment of the present invention. Rotation  805  moves steam bubbles  803 ,  804  in a circular cutting path  806  around the fiber  801  to improve cutting and removal of targeted material. Although tilted tip  802  is 45 degrees, in other embodiments, a different angled tip may create a different circular cutting path in other embodiments. 
         [0060]      FIG. 9  is a diagram of an optical fiber  901  with a tip  902  with a tilt angle of 50 degrees, in accordance with an embodiment of the present invention. In  FIG. 9A , when surrounded by air or water, the tilt angle of tip  902  exceeds the critical angle. Thus, in both situations most of the light exits through the side of the fiber  901  due to internal reflection. Consequently, only a single steam bubble  903  is formed out the side of the fiber  901 . 
         [0061]      FIG. 9B  is a diagram of optical fiber  901  with fiber rotation  904 , in accordance with an embodiment of the present invention. Rotation  904  moves steam bubble  903  in a circular cutting path  905  around the fiber  901  to improve the cutting reach of the steam bubble  903 . 
         [0062]    In some embodiments, the size of the resulting steam bubbles may be altered by changing the input angle of the laser energy into the fiber. If the laser light is input into the fiber with a small divergence from the neutral axis of the fiber, laser light will tend to exit the end of the fiber. If the laser light is input into the fiber with a small divergence at an angle with respect the axis of the fiber, the light will tend to exit the side of the fiber. 
         [0063]      FIG. 10  illustrates an embodiment of the present invention where the steam bubble is deflected from the axis of the fiber by incorporating a laser source with high water absorption (not shown), a bent optical fiber  1001 , and a tilted tip  1002 . In  FIG. 10A , the deflection angle  1004  of the steam bubble  1003  may be added to the bend angle  1005  of the fiber  1001 . The total angle of the steam bubble  1003  relative to the start of the fiber  1001  is the sum of the deflection angle  1004  and the fiber bend angle  1005 . In some embodiments, the bend angle  1005  may be maintained by a bent tube around the bent optical fiber  1001 . 
         [0064]      FIG. 10B  illustrates the use of bent optical fiber  1001  and tilted tip  1002  with a rotation  1006 . With rotation  1006 , the net deflection angle of the steam bubble  1003  may be modified from the sum of fiber bend angle  1005  and deflection angle  1004  to the net of the deflection angle  1004  subtracted from fiber bend angle  1005  by rotation of the fiber. In  FIG. 10 , the deflection angle  1004  is 20 degrees. Other embodiments may have different deflection angles and bend angles. Different angles create different circular cutting paths should the fiber be rotated. In some embodiments, where bent optical fiber  1001  is enclosed by a bent outer tube, a circular cutting path may be created by axially rotating the bent outer tube, which yields more net deflection angles and accesses more operative regions. 
         [0065]      FIG. 11  illustrates an embodiment of the present invention where the steam bubble is deflected at an angle of 35 degrees from the axis of the fiber by incorporating a laser source with high water absorption (not shown), a bent optical fiber  1101 , and a tilted tip  1102 . Similar to  FIG. 10A , in  FIG. 11A , the deflection angle  1104  of the steam bubble  1103  is added to the bend angle  1105  of the fiber  1101 . The total angle of the steam bubble  1103  relative to the start of the fiber  1101  is the sum of the deflection angle  1104  and the fiber bend angle  1105 . In some embodiments, the bend angle  1105  may be maintained by a bent tube around the bent optical fiber  1101 . 
         [0066]      FIG. 11B  illustrates the use of bent optical fiber  1101  and tilted tip  1102  with a rotation  1106 . In  FIG. 11B , the net deflection angle of the steam bubble  1103  may be modified by rotation of the fiber  1101 . In some embodiments, where bent optical fiber  1101  is enclosed by a bent outer tube, a circular cutting path may be created by axially rotating the bent outer tube to yield even more net deflection angles and access different operative regions. 
         [0067]      FIG. 12  illustrates an embodiment of the present invention where the steam bubble is deflected from the axis of the fiber by incorporating a laser source with high water absorption, a bent optical fiber, and a tilted end at the fiber. In  FIG. 12A , because the tilt angle of the tip  1202  is less than the critical angle, steam bubbles  1203 ,  1206  are formed from both the tilted tip  1202  and the side of the tip of the fiber  1201 . The deflection angle  1204  of the steam bubbles are added to the bend angle  1205  of the fiber  1201 . Combined with bend angle  1205 , the steam bubble  1206  may be directed behind the tip  1202 . In some embodiments, this provides an advantage of being able to cut material behind corners or behind the tip  1202  of the fiber  1201 . In some embodiments, the bend angle  1205  may be maintained by a bent tube around the bent optical fiber  1201 . 
         [0068]      FIG. 12B  illustrates the use of fiber  1201  and tilted tip  1202  with rotation  1207 . In  FIG. 12B , the rotation  1207  of fiber  1201  produces cutting paths  1208  and  1209  in front of and along the side of the fiber due to the combination of the steam bubbles  1203  and  1206 . These cutting paths have the advantage of removing a large volume of material in a single rotation. In some embodiments, where bent optical fiber  1201  is enclosed by a bent outer tube, a circular cutting path may be created by axially rotating the bent outer tube to yield even more net deflection angles and access different operative regions. 
         [0069]      FIG. 13  illustrates an embodiment of the present invention where the resulting steam bubble exits from the side from a bent optical fiber with a tilted end at the fiber. In  FIG. 13A , the tilt angle  1302  of the tip  1302  exceeds the critical angle, resulting in a steam bubble  1303  that exits from the side of the fiber  1301 . In some embodiments, the bend angle  1304  may be maintained by a bent tube around the bent optical fiber  1301 . 
         [0070]      FIG. 13B  illustrates the use of fiber  1301 , tilted tip  1302 , and steam bubble  1303  with rotation  1305 , in accordance with an embodiment of the present invention. In this embodiment, rotation  1305 , in combination with the bend angle  1304  and the length of the steam bubble  1303 , produces a wide cutting path  1306 . In some embodiments, where bent optical fiber  1301  is enclosed by a bent outer tube, a circular cutting path may be created by axially rotating the bent outer tube to yield even more net deflection angles and access different operative regions. 
         [0071]    The bending of the fiber can be achieved by numerous methods, such as pre-bent glass fibers and fibers bent in an outer tube. In some embodiments, bend fibers may be dynamically controlled. In certain embodiments, those bend fibers may be dynamically bent in a robotically controlled tube mechanism. In other embodiments, the fibers may be bent by a robotically controlled flexure mechanism. 
         [0072]    The present invention is not limited to embodiments using the aforementioned systems and the associated instrument drive mechanisms. One skilled in the art would appreciate modifications to facilitate coupling to different robotic arm configurations. 
         [0073]    For purposes of comparing various embodiments, certain aspects and advantages of these embodiments are described. Not necessarily all such aspects or advantages are achieved by any particular embodiment. Thus, for example, various embodiments may be carried out in a manner that achieves or optimizes one advantage or group of advantages as taught herein without necessarily achieving other aspects or advantages as may also be taught or suggested herein. 
         [0074]    Elements or components shown with any embodiment herein are exemplary for the specific embodiment and may be used on or in combination with other embodiments disclosed herein. While the invention is susceptible to various modifications and alternative forms, specific examples thereof have been shown in the drawings and are herein described in detail. The invention is not limited, however, to the particular forms or methods disclosed, but to the contrary, covers all modifications, equivalents and alternatives thereof.