Patent Publication Number: US-2023157888-A1

Title: Generating bubble jets to fragment and remove eye floaters

Description:
TECHNICAL FIELD 
     The present disclosure relates generally to laser vitreolysis systems, and more particularly to generating bubble jets to fragment and remove eye floaters. 
     BACKGROUND 
     Eye floaters are microscopic collagen fibers that can clump and cast shadows on the retina, which disturb the vision of the patient. In laser vitreolysis, a laser beam is directed into the vitreous to treat eye floaters. The laser beam may be used to disintegrate the floaters to improve vision. 
     BRIEF SUMMARY 
     In certain embodiments, an ophthalmic laser system for treating a floater in a vitreous of an eye comprises a laser device, an ophthalmic microscope, and a computer. The laser device directs laser pulses towards the floater in the vitreous of the eye. The laser device includes a laser that generates a laser beam, and a beam multiplexer that splits the laser beam into beams that form cavitation bubbles to create a bubble jet in the vitreous of the eye. The ophthalmic microscope provides an image of a shadow cast by the floater onto a retina of the eye. The computer instructs the laser device to direct the beams towards the floater in the vitreous in order to create the bubble jet to treat the floater. 
     Embodiments may include none, one, some, or all of the following features: 
     * The beam multiplexer comprises an optical device selected from the following: a diffractive optical element (DOE), a holographic optical element (HOE), a spatial light modulator (SLM), a polarizing prism, a beam amplitude splitting interferometer, a wavefront splitting interferometer, or a birefringent optical component. 
     * The beam multiplexer includes a wave plate that alters a polarization state of the laser beam, and a prism that separates the laser beam into the beams. The wave plate may be a half-wave plate that shifts the polarization state of the laser beam. The prism may be a Wollaston prism that separates the laser beam into the beams with orthogonal polarization. 
     * The beam multiplexer splits the laser beam into the beams that form the cavitation bubbles with a bubble center separation of 5 to 20 microns. 
     * The beam multiplexer creates a first cavitation bubble with a first diameter and a second cavitation bubble with a second diameter, where the second diameter is different from the first diameter. 
     * The computer instructs the laser device to direct the beams to form the cavitation bubbles arranged to direct the bubble jet in a particular direction. 
     * The computer instructs the laser device to direct the beams to form the cavitation bubbles arranged in a spiral enface pattern. 
     * The computer instructs the laser device to direct the beams to form the cavitation bubbles arranged in a raster enface pattern. 
     In certain embodiments, an ophthalmic laser system for treating a floater in a vitreous of an eye comprises a laser device, a floater detection system, and a computer. The laser device directs laser pulses towards the floater in the vitreous of the eye. The floater detection system detects the floater in the vitreous. The computer accesses a pulse pattern for the laser pulses, where the pulse pattern yields cavitation bubbles that create a bubble jet in the vitreous of the eye. The computer instructs the laser device to direct the laser pulses towards the floater according to the pulse pattern to create the bubble jet to treat the floater. 
     Embodiments may include none, one, some, or all of the following features: 
     * The computer instructs the laser device to: create a first cavitation bubble with a first diameter, and create a second cavitation bubble with a second diameter, where the second diameter is different from the first diameter. 
     * The computer instructs the laser device to direct the laser pulses to form the cavitation bubbles arranged to direct the bubble jet in a particular direction. 
     * The pulse pattern yields the cavitation bubbles with a bubble center separation of 5 to 20 microns. 
     * The pulse pattern comprises pulse groups, where each pulse group yields a set of cavitation bubbles that form a bubble jet. 
     * The pulse pattern yields the cavitation bubbles arranged in a spiral enface pattern. 
     * The pulse pattern yields the cavitation bubbles arranged in a raster enface pattern. 
     * The floater detection system configured to determine a location of the floater in the vitreous of the eye. 
     * The laser device includes a laser that generates a laser beam and a beam multiplexer that splits the laser beam into the laser pulses that form the cavitation bubbles to create the bubble jet. 
     * The ophthalmic laser system includes an xy-scanner that: receives a detection beam from the floater detection system and directs the detection beam along a detection beam path towards a floater shadow cast by the floater on a retina of the eye; and receives the laser pulses from the laser device and directs the laser pulses along the detection beam path towards the floater shadow. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    illustrates a simplified example of an ophthalmic system that creates bubble jets to fragment and remove eye floaters from an eye, according to certain embodiments; 
         FIGS.  2 A and  2 B  illustrate an example of an ophthalmic laser system with a beam multiplexer that can create cavitation bubbles to form a bubble jet, according to certain embodiments; 
         FIG.  3    illustrates an example of an ophthalmic laser surgical system with a scanner that can create cavitation bubbles to form a bubble jet, according to certain embodiments; 
         FIG.  4    illustrates an example of a laser pulse causing a floater to jump; 
         FIG.  5    illustrates an example of a bubble jet that may be created by the system of  FIGS.  2 A,  2 B, and  3   ; 
         FIG.  6    illustrates an example of a bubble jet  9  that may be created by the system of  FIGS.  2 A,  2 B, and  3   ; 
         FIGS.  7 A and  7 B  illustrate examples of a bubble jet resulting from cavitation bubbles of different diameters; 
         FIGS.  8  and  9    illustrate examples of enface pulse patterns that may be generated by the system of  FIG.  1   ; 
         FIG.  10    illustrates an example of a method for creating a bubble jet to fragment a floater, which may be performed by the system of  FIG.  1   ; and 
         FIG.  11    illustrates an example of a method for creating bubble jets to remove floater fragments, which may be performed by the system of  FIG.  1   . 
     
    
    
     DESCRIPTION OF EXAMPLE EMBODIMENTS 
     Referring now to the description and drawings, example embodiments of the disclosed apparatuses, systems, and methods are shown in detail. The description and drawings are not intended to be exhaustive or otherwise limit the claims to the specific embodiments shown in the drawings and disclosed in the description. Although the drawings represent possible embodiments, the drawings are not necessarily to scale and certain features may be simplified, exaggerated, removed, or partially sectioned to better illustrate the embodiments. 
     Laser vitreolysis can be performed to treat eye floaters in an eye. Current laser systems, however, fail to effectively and efficiently fragment and remove floaters, resulting in prolonged surgical time and retinal radiation exposure. To improve floater removal, ophthalmic systems described herein have a laser device that directs laser pulses towards a floater in the eye. The laser pulses form cavitation bubbles to create a bubble jet that fragments the floater and moves the floater fragments away from the visual field. In some examples, the laser device includes a beam multiplexer that splits a laser beam into multiple beams that form the cavitation bubbles that create the bubble jet. In some examples, the laser device directs laser pulses towards the floater according to a pulse pattern that forms the cavitation bubbles that create the bubble jet. In certain embodiments, laser device directs the pulses to yield a pattern (e.g., a spiral or raster pattern) of bubble jets. In the embodiments, some pulses block floater movement, reducing the likelihood the floater will jump. Accordingly, certain embodiments improve the effectiveness and efficiency of floater fragmentation and removal. 
     1. Example Systems 
       FIG.  1    illustrates a simplified example of an ophthalmic system  2  that creates bubble jets to treat, e.g., fragment and/or remove, eye floaters from an eye, according to certain embodiments. In the example, system  2  includes a laser device  4 , a multiplexer and/or scanner (multiplexer/scanner)  6 , and a computer  7 , coupled as shown. For ease of explanation, an axis (e.g., optical or visual axis) of the eye approximates a z-axis, which in turn defines enface planes (e.g., xy-planes) substantially orthogonal to the z-axis. An enface pulse pattern (e.g., a spiral or raster enface pulse pattern) is a pulse pattern formed on an enface plane. 
     As an overview, laser device  4  generates a laser beam comprising laser pulses. Multiplexer/scanner  6  directs the laser pulses towards the vitreous of an eye. The laser pulses cause laser-induced optical breakdowns (LIOBs) that photodisrupt the vitreous and create rapidly expanding (and contracting) cavitation bubbles  8  that may expand and contract several times. Interaction between cavitation bubbles  8  creates a bubble jet, which is a forceful jet of water. Energy of the bubbles (such as energy of internal high-pressure gas and of surface tension forces) is converted into the kinetic energy of the bubble jet. If the bubbles are of different size, the direction of motion of the bubble jet is towards the smaller bubble. The bubble jet fragments the floater and moves the floater fragments away from the visual axis, i.e., the surgeon&#39;s visual field. 
     In certain embodiments, bubbles and/or bubble jets facilitate removal of the floater fragments. For example, if the patient&#39;s head is in an upright position during surgery, the cavitation bubbles can be oriented such that the resulting bubble jet is directed towards the upper part of the posterior chamber to move fragments away from the visual field. As another example, after floater fragmentation, residual tiny bubbles become entangled in the floater fragments, and the bubbles&#39; buoyancy lift the fragments away from the visual field. As another example, after a cavitation bubble repeatedly expands and collapses a few times, the water vapor in the cavitation bubble condense into water and some gases (e.g., H 2 , O 2 , CO 2 , and NOx) remain in the bubble. These gas bubbles become entangled with the floater fragments and lift the fragments to the uppermost part of the posterior chamber, typically in about one minute. After several minutes, the gas bubbles have been absorbed into the vitreous, and the fragments have moved away from the visual field. 
     Turning to the components, laser device  4  may comprise any suitable ultrashort (e.g., nanosecond, picosecond, or femtosecond) pulse laser device. Examples of laser device  22  include YAG lasers (e.g., a Q-switched nanosecond YAG laser, such as a frequency doubled Q-switched nanosecond YAG laser), picosecond lasers (e.g., a mode-locked picosecond laser operating in the 1 to 1.1 micron (μm) spectral range or their second harmonics or an ultrashort infrared (700 to 1500 nanometers (nm)) picosecond laser), femtosecond lasers (e.g., an infrared, an ultrashort infrared (700 to 1500 nanometers (nm)), or ultraviolet femtosecond laser), and single pulse to high repetition rate (10 megahertz (MHZ)) lasers. The laser beam may have any suitable wavelength (e.g., 400 to 2000 nanometers (nm)) and focal point (e.g., 3 to 10 microns (μm), such as 5 to 6 microns). The pulses may have any suitable duration (e.g., 20 femtoseconds (fs) to 1000 nanoseconds (ns)), repetition rate (e.g., 25 to 100 kilohertz (kHz), such as 50 kHz), and pulse energy (e.g., 1 microjoule (μJ) to 1 millijoule (mJ), such as 1 to 20 μJ or 1 to 10 μJ). 
     Multiplexer/scanner  6  may comprise a multiplexer and/or scanner. A multiplexer comprises any suitable optical device that can split (or otherwise modulate) the laser beam to yield multiple laser beams, where each beam creates a cavitation bubble in the vitreous. In general, an optical device is a component that can act on (e.g., transmit, reflect, refract, diffract, collimate, condition, shape, focus, modulate, and/or otherwise act on) light. Examples of beam multiplexers include a diffractive optical element (DOE) (e.g., a diffraction grating), a holographic optical element (HOE), a spatial light modulator (SLM) (e.g., an electrically addressable SLM), a polarizing prism (e.g., a Wollaston, Normarski, Rochon, or Senamont prism), a beam amplitude splitting interferometer (e.g., a Michelson, Mach-Zender, or Fizeau wedge interferometer), a wavefront splitting interferometer (e.g., a Lloyd mirror or Fresnel biprism), a birefringent optical component, or a combination of different beam multiplexers (e.g., 5× diffractive multiplexer and a Wollaston-doubler). 
     A scanner moves focal point of the laser beam to different locations of an enface plane to create cavitation bubbles in the vitreous. Examples of scanners include a galvo scanner (e.g., a pair of galvanometrically-actuated scanner mirrors that can be tilted about mutually perpendicular axes), an electro-optical scanner (e.g., an electro-optical crystal scanner) that can electro-optically steer the beam, or an acousto-optical scanner (e.g., an acousto-optical crystal scanner) that can acousto-optically steer the beam. 
     In the example, the pulses create any suitable number (e.g., two, three, four, or more) of cavitation bubbles  8 . Cavitation bubbles  8  may be formed any suitable spatial and temporal distance apart that allows bubbles  8  to interact (e.g., come into contact) with each other. The spatial pulse separation may be selected according to the bubble diameter, which may be 150 micrometers (μm) to 2 millimeters (mm), depending on pulse energy. For example, a 10 microjoule (μJ) pulse may yield a 150 to 300 μm diameter; a 6 μJ pulse may yield a 254 μm diameter; and 1 mJ pulse may yield a 1 mm diameter. If a scanner forms cavitation bubbles  8 , the scan rate (which determines the temporal separation) may be selected according to the lifetime of bubbles to yield bubbles that are sufficiently temporally close to interact. For example, the bubble lifetime may be approximately 0.1 to 0.3 milliseconds (ms). A scan rate of 50 kilo hertz (kHz) forms bubbles every 1/50 kHz=20 microseconds (μs), so neighboring bubbles are inflated long enough to interact. 
     Computer  7  controls components of system  2  in accordance with computer programs. For example, computer  7  instructs laser device  4  and multiplexer/scanner  6  focus laser pulses at the vitreous to create a bubble jet to fragment a floater or remove floater fragments. 
     1.1 Laser-Slit Lamp System 
       FIGS.  2 A and  2 B  illustrate an example of an ophthalmic laser system  10  with a beam multiplexer that can create cavitation bubbles to form a bubble jet, according to certain embodiments.  FIG.  2 A  illustrates an example of ophthalmic laser system  10  with a beam multiplexer.  FIG.  2 B  illustrates an example of a beam multiplexer comprising a beam doubler  60  that may be used in system  10  of  FIG.  2 A . 
     In the example, ophthalmic laser system  10  allows an operator (with an operator eye  12 ) to see a floater within a patient eye  14 . Ophthalmic laser system  10  comprises oculars  20 , a laser delivery head  22 , a slit illumination source  26 , a positioning device (such as a joystick  28 ), a base  30 , and a console  32 , coupled as shown. Laser delivery head  22  includes a laser fiber  34 , a zoom system  36 , a collimator  38 , a beam multiplexer  39 , a mirror  40 , and an objective lens  42 , coupled as shown. Slit illumination source  26  includes a light source  43 , condenser lens  44 , a variable aperture  45 , a variable slit plate  46 , a projection lens  47 , and a mirror  48 , coupled as shown. Console  32  includes a computer  50 , a laser  52 , and a user interface  54 , coupled as shown. 
     As an overview, ophthalmic laser system  10  includes a laser device  16  (e.g., laser  52 , laser fiber  34 , and laser delivery head  22 ) and an ophthalmic microscope  18 , which includes a slit lamp (e.g., oculars  20 , objective lens  42 , mirror  48 , and slit illumination source  26 ). Operator eye  12  utilizes the optical path from oculars  20  through mirror  40 , objective lens  42 , and mirror  48  to view patient eye  14 . A laser beam follows the laser path from laser  52  through laser delivery head  22  and mirror  48  to treat patient eye  14 . 
     According to the overview, laser device  16  directs a laser beam comprising laser pulses towards a floater within eye  14 . Ophthalmic microscope  18  gathers light reflected from within eye  14  to yield an image of eye  14 . Laser beam multiplexer  39  multiplexes (e.g., splits or otherwise modulates) the laser beam into beams that form a cavitation bubbles in the vitreous, and may be any suitable multiplexer as described with reference to  FIG.  1   . Computer  50  instructs laser device  16  to direct the laser pulses towards the vitreous to form cavitation bubbles that create a bubble jet. 
     In more detail, in certain embodiments, oculars  20  allow operator eye  12  to view patient eye  14 . Laser delivery head  22  delivers a laser beam of laser pulses from laser  52  through laser fiber  34  to patient eye  14 . Laser  52  is any suitable laser that generates a laser beam as described with reference to  FIG.  1   . Zoom system  36  changes the spot size of the laser beam that exits fiber  34 . Collimator  38  collimates the laser beam, and mirror  40  directs the beam through objective lens  42 , which focuses the beam. Zoom system  36  and collimator  38  direct a parallel laser beam to mirror  40  to focus the laser beam onto the image plane of ophthalmic microscope  18 . Mirror  40  may be a dichroic mirror that is reflective for the laser beam wavelength and transmissive for visible light. 
     Slit illumination source  26  of laser system  10  provides light that illuminates the surgical site of patient eye  14 . Slit illumination source  26  includes light source  43 , which emits light such as a high-intensity illumination light. Condenser lens  44  directs the light towards variable aperture  45  and variable slit plate  46 . Variable aperture  45  defines the height of the light in the y-direction, and variable slit plate  43  defines the width of the light in the x-direction to form the light into a slit shape. Projection lens  47  directions the light towards prism mirror  48 , which directs the slit of light into patient eye  14 . 
     Base  30  supports laser delivery head  22  and slit illumination source  26 . Joystick  28  moves base  30 . Console  32  includes components that support the operation of system  10 . Computer  50  of console  32  controls of the operation of components of system  10 , e.g., base  30 , laser delivery head  22 , slit illumination source  26 , laser  52 , and/or user interface  54 . User interface  54  communicates information between the operator and system  10 . 
       FIG.  2 B  illustrates an example of a beam multiplexer comprising a beam doubler  60 . Beam doubler  60  splits a laser beam into a plurality of beams, which are directed to objective lens  42 . At objective lens  42 , beams have different intensities I 1 , I 2 , which yield cavitation bubbles  8  ( 8   a ,  8   b ) of different diameters. In the example, intensity I 1  is greater than intensity I 2  and yields a bubble  8   a  with a greater diameter than that of bubble  8   b . As described above, the direction of motion of the bubble jet is towards the smaller bubble. In other examples, cavitation bubbles  8  may have substantially the same diameter. 
     In the example, beam doubler  60  includes a wave plate  62 , e.g., a half-wave plate, and a prism  64 , e.g., a Wollaston prism. Wave plate  62  is an optical device that alters the polarization state of a light wave travelling through it. In the example, a half-wave plate shifts the polarization direction of linearly polarized light. Prism  64  is a transparent optical device with flat surfaces that refract light. At least one surface is angled (not parallel) to another surface. A Wollaston prism separates light into two orthogonally linearly polarized beams that yield two bubbles. Prism  64  may have any suitable separation, e.g., 0.2 to 5.0 degrees, to yield bubbles with any suitable bubble center separation, e.g., 0.1 to 3.0 millimeters (mm). For example, 2 millijoule (mJ) laser pulses yield bubbles with diameters of around 1.8 mm. A prism separation of 0.5 degrees results in a bubble center separation of 160 mm*sin (0.5)=1.4 mm, which is close enough to allow the bubbles to interact. 
     The intensity ratio I 1 /I 2  of the bubbles (and thus the relative diameters of the bubbles) can be changed by adjusting, e.g., rotating, wave plate  62  and/or prism  64 . That is, wave plate  62  can create cavitation bubble with different intensities and different diameters. Since the direction of the bubble jet is towards the smaller bubble, wave plate  62  may be used to adjust the direction of the bubble jet. 
     1.2 Floater Detection-Laser System 
       FIG.  3    illustrates an example of an ophthalmic laser surgical system  110  with a scanner that can create cavitation bubbles to form a bubble jet, according to certain embodiments. As an overview, system  110  includes a floater detection system  120 , a laser device  122 , one or more shared components  124 , and a computer  126 , coupled as shown. Laser device  122  includes a laser  130  and a z-scanner  132 , coupled as shown. Shared components  124  include an xy-scanner  140 , an xy-encoder  141 , and optical elements (such as a mirror  142  and lenses  144  and  146 ), coupled as shown. Computer  126  includes logic  150 , a memory  152  (which stores a computer program  154 ), and a display  156 , coupled as shown. 
     As an overview of operation of system  110 , floater detection system  120  directs a detection beam along a detection beam path towards an eye and determines the location of the floater. Laser device  122  receives the z-location of the floater relative to the retina from the floater detection system and directs a laser beam along a laser beam path towards the z-location of the floater. Shared component xy-scanner receives the detection beam and directs the detection beam along the detection beam path towards the floater. Xy-scanner  140  also receives the laser beam from the laser device and directs the laser beam along the same detection beam path towards the floater. 
     Turning to the parts of the system, floater detection system  120  includes one or more detection devices that detect a floater in an eye. To detect a floater, a detection device directs a detection beam towards the eye, detects the beam reflected from the eye, and detects the floater using the reflected beam. The device may detect the floater from the reflected beam by sensing a change in the beam that indicates the presence of a floater or by generating an image of the floater or the floater&#39;s shadow on the retina (“floater shadow”), which may be displayed on display  156 . The devices may utilize the same or different technologies, e.g., scanning laser ophthalmoscopy (SLO) and/or optical coherence tomography (OCT). One or more detection devices may provide the x, y, and/or z locations of the floater. 
     Laser device  122  includes laser  130 , which generates a laser beam comprising laser pulses. Laser  130  may comprise any suitable laser as described with reference to  FIG.  1   , e.g., a femtosecond laser. Z-scanner  132  longitudinally directs the focal point of the laser beam to a specific location in the z-direction. In certain embodiments, laser device  122  includes a multiplexer that multiplexes a laser beam to yield multiple cavitation bubbles that create a bubble jet. The multiplexer may be any suitable multiplexer as described with reference to  FIG.  1   . 
     Shared components  124  direct detection and laser beams from floater detection system  120  and laser device  122 , respectively, towards the eye. Because detection and laser beams both use shared components  124 , both beams are affected by the same optical distortions. Accordingly, when the detection beam is used to aim the laser beam, the distortions are canceled out, which improves the accuracy of the laser beam. As an example of operation, mirror  142  directs a beam towards xy-scanner  140 , which transversely directs the focal point of the laser beam in the x- and y-directions towards lens  144 . Xy-scanner  140  may comprise any suitable scanner as described with reference to  FIG.  1   . Lenses  144  and  146  direct the beam towards eye. Xy-encoder  141  detects the position of xy-scanner  140  and reports the position in encoder units to floater detection system  120 , laser device  122 , and/or computer  26 . Shared components  124  may also provide spectral and polarization coupling and decoupling of detection and laser beams to allow the beams to share the same path. 
     Computer  126  controls components of system  110  in accordance with computer program  154 . For example, computer  126  controls components (e.g., floater detection system  120 , laser device  122 , and shared components  124 ) to detect a floater and focus a laser beam at the floater. Computer  126  may be separated from components or may be distributed among system  110  in any suitable manner, e.g., within floater detection system  120 , laser device  122 , and/or shared components  124 . In certain embodiments, portions of computer  126  that control floater detection system  120 , laser device  122 , and/or shared components  124  may be part of floater detection system  120 , laser device  122 , and/or shared components  124 , respectively. 
     2. Floaters 
       FIG.  4    illustrates an example of a laser pulse causing a floater  210  to jump. If the pulse hits the center of floater  210 , the bubble fragments floater  210 . However, if the pulse hits the periphery of floater  210 , the bubble rapidly pushes floater  210 , causing it to jump. If floater  210  jumps a distance of, e.g., 1 millimeter (mm), the laser will have to be redirected with the positioning device. 
     In certain embodiments, system  2  may create a laser pulse pattern that reduces the likelihood of causing a floater to jump. The pattern places pulses in the path where floater  210  could jump (e.g., outside the area of floater  210 ) in order to limit the movement of floater  210 . That is, the coverage of the pulse pattern (i.e., the area enclosed by the outermost pulses of the pulse pattern) may be substantially centered about the centroid of floater  210  and may be larger than at least a majority of floater  210 . 
     3. Bubble Jets 
       FIG.  5    illustrates an example of a bubble jet  9  that may be created by ophthalmic laser system  10  and  110  of  FIGS.  2 A,  2 B, and  3   . In the example, ophthalmic laser system  10  forms cavitation bubbles  8  that create bubble jet  9 . For example, a low repetition rate (e.g., less than 3 pulses per second (pps)) laser device with a beam multiplexer may form bubble jet  9 . Cavitation bubbles  8  include a larger bubble  8   a  and a smaller bubble  8   b . The direction of motion of bubble jet  9  is towards smaller bubble  8   b . The direction may be determined by a line drawn through the centers of bubbles  8 , from the larger bubble  8   a  towards the smaller bubble  8   b.    
       FIG.  6    illustrates an example of a bubble jet  9  that may be created by ophthalmic laser system  10  and  110  of  FIGS.  2 A,  2 B, and  3   . In the example, ophthalmic laser system  10  creates cavitation bubbles  8  ( 8   a ,  8   b ) along a scan line  11  indicating where the scanner scans. Bubble  8   b  is created after bubble  8   a  at a distance where bubbles  8  can coalesce. Cavitation bubbles  8  interact to create a bubble jet  9  that propagates tangentially to the track of scan line  11 . 
       FIGS.  7 A and  7 B  illustrate examples of a bubble jet  224  resulting from cavitation bubbles  220  ( 220   a ,  220   b ) of different diameters, where bubble  220   a  is larger than bubble  220   b . Cavitation bubbles  220  ( 220   a ,  220   b ) maybe formed any suitable distance apart that allows bubbles  220  to interact, e.g., 5 to 20 microns, such as approximately 10 microns apart. Interaction between cavitation bubbles  220   a  and  220   b  form bubble jet  224  that flows towards the smaller bubble  220   b.    
     4. Pulse Patterns 
       FIGS.  8  and  9    illustrate examples of enface pulse patterns  230  ( 230   a  and  230   b ) that may be generated by system  10  of  FIG.  1   . Pulse patterns  230  create bubble jets that fragment a floater and/or remove floater fragments. In the examples, pulse patterns  230  include pulse groups, where each pulse group yields a bubble group  222  with cavitation bubbles proximate to each other to create a bubble jet. Pulse patterns  230  may have any suitable size or shape in two- or three-dimensions, and a bubble group  222  may have any suitable number of bubbles. In certain embodiments, the enface coverage of a pattern  230  may cover the enface dimension of the floater. In certain cases (e.g., for a thick floater), multiple enface patterns  230  may be applied at different depths, yielding a three-dimensional pattern  230 . 
     Pulse patterns  230  may be formed in any suitable manner. For example, a medium repetition rate (e.g., 100 Hz to 10 kHz) picosecond or femtosecond laser with a beam multiplexer can create a pulse pattern  230 . In the example, the laser pulse energy per spot is 20 μJ, and the corresponding bubble oscillation period is T=13.3 us*20 1/3 =36.1 μs. The repetition rate of 100 to 10 kHz corresponds to a pulse separation of 100 to 10,000 μs. In this example, the previous bubble group  222  disappears before the next pulse group arrives, so there is no interaction between the pulse group and the remains of the previous bubble group  222 . 
     As another example, a high repetition rate (e.g., 40 to 150 kHz) picosecond or femtosecond laser with a beam multiplexer can create a pulse pattern  230 . In the example, the pulse energy is 20 μJ per spot, the repetition rate is 40 kHz, and the pulse separation time is 25 μs. Thus, the next pulse group arrives when the previous bubble group  222  (or re-bouncing bubbles) still exist (or are living or alive). Under these conditions, different bubble groups  222  interact to yield a multi-group interaction, e.g., two groups of two bubbles yield a four-bubble interaction. The multi-group interaction creates bubbles jets to fragment a floater and/or remove floater fragments. 
     As another example, a high repetition rate (e.g., 40 to 150 kHz) laser creates a pulse pattern  230 . In the example, pulse pattern is a spiral scan that starts at the center of the visual field to fragment a floater and move the floater fragments away from the visual field. The spiral has a large (e.g., 50 um) tangential spot separation, the laser pulse energy per spot is 20 μJ, and the corresponding bubble oscillation period is T=13.3 us*20 1/3 =36.1 μs. The repetition rate of 40 to 150 kHz corresponds to a pulse separation of 6.67 to 25 us. Thus, the next pulse arrives when the previous cavitation bubble still exists to form a bubble jet. The direction of the jet is tangential to the spiral, and the length of the jet may be as long as several millimeters. 
     4.1 Spiral Pulse Patterns 
       FIG.  8    illustrates an example of a spiral pulse pattern  230   a . Spiral pulse pattern  230   a  includes a spiral pattern of pulse groups that yield bubble groups  222 , where each bubble group  222  is designed to yield a bubble jet  224 . In the example, bubble jets  224  are created with jets pointing in the same direction to optimize the kinetic energy of bubble jets  224 . Spiral pulse pattern  230   a  may be created with any suitable number of pulses (e.g., 10 to 1000 pulses), tangential spot separation (e.g., 2 to 100 μm), and radial spot separation (e.g., 2 to 200 μm). 
     4.2 Raster Pulse Patterns 
       FIG.  9    illustrates an example of a raster pulse pattern  230   b . Raster pulse pattern  230   b  includes a raster pattern of pulse groups that yield bubble groups  222 , where each bubble group  222  is designed to yield a bubble jet  224 . In the example, bubble jets  224  are created with jets pointing in the same direction to optimize the kinetic energy of bubble jets  224 . The raster pattern is formed by scanning in one direction to form a row of pulses, turning around at the end of the row, and then scanning in the opposite direction proximate to the previous row to form the next row of pulses. Raster pulse pattern  230   b  may be created with any suitable number of pulses (e.g., 10 to 1000 pulses), spot separation in the same row (e.g., 2 to 100 μm), and row separation (e.g., 2 to 200 μm). 
     5. Example Methods 
       FIG.  10    illustrates an example of a method for creating a bubble jet to fragment a floater, which may be performed by system  10  of  FIG.  1   . The method starts at step  310 , where a computer instructs a laser device to fragment the floater. The laser device generates a laser beam at step  312 . The laser beam may comprise laser pulses such as femtosecond pulses. The laser beam is multiplexed and/or scanned at step  314  to yield multiple cavitation bubbles in the vitreous. 
     The laser pulses form cavitation bubbles at step  316  to create a bubble jet. The bubbles may have different (or the same) diameters. In certain embodiments, the cavitation bubbles are arranged to direct the bubble jet in a particular direction, e.g., in the direction of the smaller bubble. The cavitation bubbles create the bubble jet at step  318  to fragment the floater. 
       FIG.  11    illustrates an example of a method for creating bubble jets to remove floater fragments, which may be performed by system  10  of  FIG.  1   . The method starts at step  410 , where a computer accesses a pulse pattern for a laser device. The pulse pattern may be designed to control the direction of the floater fragment removal. The computer instructs the laser device to direct laser pulses towards a floater according to the pulse pattern at step  412 . 
     The pulses form cavitation bubbles at step  414 . In certain embodiments, the cavitation bubbles are arranged to create bubble jets that point in one or more directions that facilitate removal of the fragments. The cavitation bubbles create bubble jets to remove floater fragments at step  420 . The forces of the bubble jets move the fragments away from the visual axis. In addition, after some bubbles collapse, longer-living gas bubbles become entangled in the fragments and move them away from the visual axis. 
     A component (such as a control computer) of the systems and apparatuses disclosed herein may include an interface, logic, and/or memory, any of which may include computer hardware and/or software. An interface can receive input to the component and/or send output from the component, and is typically used to exchange information between, e.g., software, hardware, peripheral devices, users, and combinations of these. A user interface is a type of interface that a user can utilize to communicate with (e.g., send input to and/or receive output from) a computer. Examples of user interfaces include a display, Graphical User Interface (GUI), touchscreen, keyboard, mouse, gesture sensor, microphone, and speakers. 
     Logic can perform operations of the component. Logic may include one or more electronic devices that process data, e.g., execute instructions to generate output from input. Examples of such an electronic device include a computer, processor, microprocessor (e.g., a Central Processing Unit (CPU)), and computer chip. Logic may include computer software that encodes instructions capable of being executed by an electronic device to perform operations. Examples of computer software include a computer program, application, and operating system. 
     A memory can store information and may comprise tangible, computer-readable, and/or computer-executable storage medium. Examples of memory include computer memory (e.g., Random Access Memory (RAM) or Read Only Memory (ROM)), mass storage media (e.g., a hard disk), removable storage media (e.g., a Compact Disk (CD) or Digital Video or Versatile Disk (DVD)), database, network storage (e.g., a server), and/or other computer-readable media. Particular embodiments may be directed to memory encoded with computer software. 
     Although this disclosure has been described in terms of certain embodiments, modifications (such as changes, substitutions, additions, omissions, and/or other modifications) of the embodiments will be apparent to those skilled in the art. Accordingly, modifications may be made to the embodiments without departing from the scope of the invention. For example, modifications may be made to the systems and apparatuses disclosed herein. The components of the systems and apparatuses may be integrated or separated, or the operations of the systems and apparatuses may be performed by more, fewer, or other components, as apparent to those skilled in the art. As another example, modifications may be made to the methods disclosed herein. The methods may include more, fewer, or other steps, and the steps may be performed in any suitable order, as apparent to those skilled in the art. 
     To aid the Patent Office and readers in interpreting the claims, Applicants note that they do not intend any of the claims or claim elements to invoke 35 U.S.C. § 112(f), unless the words “means for” or “step for” are explicitly used in the particular claim. Use of any other term (e.g., “mechanism,” “module,” “device,” “unit,” “component,” “element,” “member,” “apparatus,” “machine,” “system,” “processor,” or “controller”) within a claim is understood by the applicants to refer to structures known to those skilled in the relevant art and is not intended to invoke 35 U.S.C. § 112(f).