US20070078379A1 - Controlling a phacoemulsification surgical system by transitioning between pulse and burst modes - Google Patents

Abstract

Methods of manipulating pulses of ultrasonic energy for use with an ophthalmic surgical device.

Description

FIELD OF THE INVENTION
• The present invention relates generally to the field of ophthalmic surgery and, more particularly, to a method of manipulating the shapes, sequences and durations of pulses of ultrasonic energy generated by an ultrasound handpiece of a phacoemulsification surgical system.
BACKGROUND
• The human eye functions to provide vision by transmitting light through a clear outer portion called the cornea, and focusing the image by way of a lens onto a retina. The quality of the focused image depends on many factors including the size and shape of the eye, and the transparency of the cornea and lens. When age or disease causes the lens to become less transparent, vision deteriorates because of the diminished light that can be transmitted to the retina. This deficiency is medically known as a cataract. An accepted treatment for cataracts is to surgically remove the cataract and replace the lens with an artificial intraocular lens (IOL). In the United States, the majority of cataractous lenses are removed using a surgical technique called phacoemulsification. During this procedure, a thin cutting tip or needle is inserted into the diseased lens and vibrated ultrasonically. The vibrating cutting tip liquefies or emulsifies the lens, which is aspirated out of the eye. The diseased lens, once removed, is replaced by an IOL.
• A typical ultrasonic surgical device suitable for an ophthalmic procedure includes an ultrasonically driven handpiece, an attached cutting tip, an irrigating sleeve or other suitable irrigation device, and an electronic control console. The handpiece assembly is attached to the control console by an electric cable or connector and flexible tubings. A surgeon controls the amount of ultrasonic energy that is delivered to the cutting tip of the handpiece and applied to tissue by pressing a foot pedal to request power up to the maximum amount of power set on the console. Tubings supply irrigation fluid to and draw aspiration fluid from the eye through the handpiece assembly.
• The operative part of the handpiece is a centrally located, hollow resonating bar or horn that is attached to piezoelectric crystals. The crystals are controlled by the console and supply ultrasonic vibrations that drive both the horn and the attached cutting tip during phacoemulsification. The crystal/horn assembly is suspended within the hollow body or shell of the handpiece by flexible mountings. The handpiece body terminates in a reduced diameter portion or nosecone at the body's distal end. The nosecone is externally threaded to accept the irrigation sleeve. Likewise, the horn bore is internally threaded at its distal end to receive the external threads of the cutting tip. The irrigation sleeve also has an internally threaded bore that is screwed onto the external threads of the nosecone. The cutting tip is adjusted so that the tip projects only a predetermined amount past the open end of the irrigating sleeve.
• In use, the ends of the cutting tip and the irrigating sleeve are inserted into a small incision in the cornea, sclera, or other location. One known cutting tip is ultrasonically vibrated along its longitudinal axis within the irrigating sleeve by the crystal-driven ultrasonic horn, thereby emulsifying the selected tissue in situ. The hollow bore of the cutting tip communicates with the bore in the horn that in turn communicates with the aspiration line from the handpiece to the console. Other suitable cutting tips include piezoelectric elements that produce both longitudinal and torsional oscillations. One example of such a cutting tip is described in U.S. Pat. No. 6,402,769 (Boukhny), the contents of which are incorporated herein by reference.
• A reduced pressure or vacuum source in the console draws or aspirates emulsified tissue from the eye through the open end of the cutting tip, the cutting tip and horn bores and the aspiration line, and into a collection device. The aspiration of emulsified tissue is aided by a saline solution or other irrigant that is injected into the surgical site through the small annular gap between the inside surface of the irrigating sleeve and the cutting tip.
• One known technique is to make the incision into the anterior chamber of the eye as small as possible in order to reduce the risk of induced astigmatism. These small incisions result in very tight wounds that squeeze the irrigating sleeve tightly against the vibrating tip. Friction between the irrigating sleeve and the vibrating tip generates heat. The risk of the tip overheating and burning tissue is reduced by the cooling effect of the aspirated fluid flowing inside the tip.
• Some known surgical systems use “pulse mode” in which the amplitude of fixed-width pulses can be varied using a controller, such as a foot pedal. Other known surgical systems utilize “burst mode” in which each pulse of a series of periodic, fixed width, constant amplitude pulses is followed by an “off” time. The off time can be varied using a controller. Other known systems use pulses having an initial maximum power level followed by a lower power level. For example, Publication No. PCT/US2004/007318 describes pulses that rise from zero to an initial, maximum power level, and then subsequently decrease to lower levels.
• While known surgical systems have been used effectively, they can be improved by allowing greater control over pulses for use with various surgical devices and applications. For example, known systems that use square or rectangular pulses typically have power levels that increase very quickly to a maximum power level. Sharp pulse transitions can reduce the ability to hold and emulsify lens material. More specifically, when lens material is held at a tip of an ultrasound hand piece by vacuum, the very fast (almost immediate) ramping of a pulse to a maximum power level can displace or push the lens material away from the tip too quickly. This, in turn, complicates cutting of the lens material. In other words, rapid power transitions can create an imbalance between vacuum at the ultrasonic tip that holds or positions the lens material and the ability to emulsify lens material.
• Other known systems operate at high power levels when less power or no power would suffice. For example, with rectangular pulses, an initial high power level may be needed to provide power to emulsify lens material. However, after the material is pushed away or emulsified, additional power may not be needed. Rectangular pulses that apply the same amount of power after movement or emulsification of lens material can result in excessive heat being applied to tissue, which can harm the patient.
• Further, pulse patterns that are used by some known surgical systems do not adequately reduce cavitation effects. Cavitation is the formation of small bubbles resulting from the back and forth movement of an ultrasonic tip. This movement causes pockets of low and high pressure. As the ultrasonic tip moves backwards, it vaporizes liquid due to a low local pressure and generates bubbles. The bubbles are compressed as the tip moves forwards and implode. Imploding bubbles can create unwanted heat and forces and complicate surgical procedures and present dangers to the patient.
• Therefore, a need continues to exist for methods that allow pulse shapes and durations to be manipulated for different phacoemulsification applications and procedures.
SUMMARY
• In accordance with one embodiment of the invention, a method of generating ultrasonic energy for use with an ophthalmic surgical device includes generating pulses having an on-time, a first off-time, and a first amplitude. The first off-time is greater than the on-time. The method includes reducing the first off-time of the pulses and increasing the amplitude of the pulses from the first amplitude to a second amplitude when the first off-time is reduced to a pre-determined second off-time.
• The first off-time can be reduced in response to a controller, such as a foot pedal. The first off-time can be reduced until the foot pedal reaches a pre-determined position corresponding to a certain off-time of the pulses, after which the off-time remains constant. The amplitude of the pulses is increased after the pre-determined second off-time is about the same as the on-time in response to the foot pedal. The off-time and the amplitude can be adjusted with continuous movement of a single controller.
• In accordance with another embodiment of the invention, a method of generating ultrasonic energy for use with an ophthalmic surgical device includes generating burst mode pulses and transforming burst mode pulses into pulse mode pulses in response to a controller.
• In accordance with a further embodiment of the invention, a method of generating ultrasonic energy for use with an ophthalmic surgical device includes generating pulse mode pulses and transforming pulse mode pulses into burst mode pulses in response to a controller.
• Transforming between burst and pulse modes can be performed in response to movement of the foot pedal and begins after the foot pedal reaches a pre-determined position. Burst mode pulses are generated by generating pulses having an on-time, a first off-time and a first amplitude. Burst mode pulses are transformed into pulse mode pulses by reducing the first off-time of the pulses to a second off-time in response to the controller. When the second off-time reaches a pre-determined value, the amplitude of the pulses is increased from the first amplitude to a second amplitude in response to the controller. The pre-determined value can be the same as the on-time or another desired value. The on-time remains constant during the transforming step.
BRIEF DESCRIPTION OF THE DRAWINGS
• Referring now to the drawings, in which like reference numbers represent corresponding parts throughout and in which:
• FIG. 1 illustrates an exemplary phacoemulsification surgical system that may be used with various embodiments;
• FIG. 2A is block diagram showing components of an exemplary phacoemulsification surgical system;
• FIGS. 2B and 2C illustrate pulses for use with a phacoemulsification surgical system;
• FIG. 3 illustrates pulses having linear rise and linear decay components and a constant maximum amplitude component according to one embodiment;
• FIG. 4 illustrates pulses having linear rise and linear decay components that meet at a maximum point according to a further embodiment;
• FIG. 5 illustrates a combination of pulses having a rectangular pulse and a pulse having a linear component according to another embodiment;
• FIG. 6 illustrates a combination of pulses having a rectangular pulse and a pulse having a linear component according to further embodiment;
• FIG. 7 illustrates a combination of pulses having a rectangular pulse and a pulse having a linear component according to yet a further embodiment;
• FIG. 8 illustrates a combination of pulses having a rectangular pulse and a pulse having a linear component at the same amplitude according to one embodiment;
• FIG. 9 illustrates pulses having linear rise and decay components, a constant amplitude component that has sequentially increasing power according to one embodiment;
• FIG. 10 illustrates pulses having linear rise and decay components that meet at a maximum point and that have sequentially increasing power according to a further embodiment;
• FIG. 11 illustrates a combination of rectangular pulses and pulses having a linear component having sequentially increasing power according to one embodiment;
• FIG. 12 illustrates pulses having linear rise and decay components, a constant amplitude component and sequentially decreasing power according to one embodiment;
• FIG. 13 illustrates pulses having linear rise and linear decay components that meet at a maximum point and having sequentially decreasing power according to a further embodiment;
• FIG. 14 illustrates a combination of rectangular pulses and pulses having a linear component and that have sequentially decreasing power according to another embodiment;
• FIG. 15 illustrates known fixed burst mode pulses;
• FIG. 16 illustrates known linear burst mode pulses;
• FIG. 17 illustrates known pulse mode pulses;
• FIG. 18 illustrates continuous transformation of burst mode pulses to pulse mode pulses in response to a controller according to one embodiment;
• FIG. 19 illustrates continuous transformation of pulse mode pulses to burst mode pulses in response to a controller according to another embodiment;
• FIG. 20 illustrates multi-segment rectangular pulses having two pulse segments with increasing amplitude according to yet another embodiment;
• FIG. 21 illustrates a multi-segment rectangular pulse according to an alternative embodiment having three pulse segments with increasing amplitude;
• FIG. 22 illustrates packets of pulses of ultrasonic energy shown inFIG. 10; and
• FIG. 23 illustrates packets of pulses of ultrasonic energy shown inFIG. 13.
DETAILED DESCRIPTION OF ILLUSTRATED EMBODIMENTS
• This specification describes embodiments of methods of manipulating pulses of ultrasonic energy to control a surgical system for use in, for example, phacoemulsification surgery. Embodiments can be implemented on commercially available surgical systems or consoles through appropriate hardware and software controls.FIGS. 1 and 2 illustrate exemplary surgical systems.
• FIG. 1 illustrates one suitable system and represents the INFINITI® Vision System available from Alcon Laboratories, Inc., 6201 South Freeway, Q-148, Fort Worth, Tex. 76134.FIG. 2A illustrates anexemplary control system100 that can be used with this system.
• Thecontrol system100 is used to operate anultrasound handpiece112 and includes a control console114, which has a control module or CPU116, an aspiration, vacuum or peristaltic pump118, ahandpiece power supply120, an irrigation flow or pressure sensor122 and avalve124.Various ultrasound handpieces112 and cutting tips can be utilized including, but not limited to, handpieces and tips described in U.S. Pat. Nos. 3,589,363; 4,223,676; 4,246,902; 4,493,694; 4,515,583; 4,589,415; 4,609,368; 4,869,715; 4,922,902; 4,989,583; 5,154,694 and 5,359,996, the contents of which are incorporated herein by reference. The CPU116 may be any suitable microprocessor, micro-controller, computer or digital logic controller. The pump118 may be a peristaltic, a diaphragm, a Venturi or other suitable pump. Thepower supply120 may be any suitable ultrasonic driver. The irrigation pressure sensor122 may be various commercially available sensors. Thevalve124 may be any suitable valve such as a solenoid-activated pinch valve. An infusion of an irrigation fluid, such as saline, may be provided by a saline source126, which may be any commercially available irrigation solution provided in bottles or bags.
• In use, the irrigation pressure sensor122 is connected to thehandpiece112 and the infusion fluid source126 throughirrigation lines130,132 and134. The irrigation pressure sensor122 measures the flow or pressure of irrigation fluid from the source126 to thehandpiece112 and supplies this information to the CPU116 through the cable136. The irrigation fluid flow data may be used by the CPU116 to control the operating parameters of the console114 using software commands. For example, the CPU116 may, through a cable140, vary the output is of thepower supply120 being sent to thehandpiece112 and the tip113 though a power cable142. The CPU116 may also use data supplied by the irrigation pressure sensor122 to vary the operation of the pump118 and/or valves through a cable144. The pump118 aspirates fluid from thehandpiece112 through aline146 and into a collection container128 throughline148. The CPU116 may also use data supplied by the irrigation pressure sensor122 and the applied output ofpower supply120 to provide audible tones to the user. Additional details concerning such surgical systems can be found in U.S. Pat. No. 6,179,808 (Boukbny, et al.) and U.S. Pat. No. 6,261,283 (Morgan, et al.), the entire contents of which are incorporated herein by reference.
• The control console114 can be programmed to control and manipulate pulses that are delivered to thehandpiece112 and, in turn, control the power of the pulses of the handpiece that is used during surgery. Referring toFIGS. 2B and 2C, the pulses are generated in packets or in on periods and off periods. In the illustrated example, the pulses have a 50% duty cycle. Indeed, various on-times, off-times and duty cycles can be used for different applications.
• The following description assumes that a maximum power level of 100% is the maximum attainable power (i.e., maximum stroke or displacement of the ultrasonic tip). In other words, 50% power refers to half of the maximum attainable power. Power levels are represented as a percentage (%) of the maximum attainable power. Embodiments of pulse manipulation that can be used with the exemplary phacoemulsification surgical system described above are illustrated inFIGS. 3-21, which can be organized as micro-bursts or packets of pulses, as shown inFIGS. 2B and 2C. The packets or bursts of pulses are provided to the ultrasound handpiece, which generates a generally corresponding output at the ultrasonic tip.
• Referring toFIG. 3, according to one embodiment, one or both of the rise anddecay components310 and312 of eachpulse300 can be programmed separately from a natural rise and natural decay. For example rise anddecay components310 and312 can be programmed with linear and/or non-linear functions separately from natural rise and decay times that occur due to switching an amplifier on and off to generate pulses. Persons skilled in the art will appreciate that some pulses (e.g., square and rectangular pulses) are typically represented as “ideal” square or rectangular pulses having immediate and sharp transitions between low and maximum power levels. In practice, however, such pulses have natural rise and decay times, e.g., exponential rise and decay times, which are caused by a load or impedance. For example, typical natural decay times can be about 4 milliseconds (ms). Embodiments, in contrast, are directed to controlling linear rise and linear decay times separately from natural transitions that are caused by switching an amplifier on and off by setting or programming the rise and/or decay functions.
• Controlling the rise anddecay components310 and312 and rise anddecay times312 and322 provides advantageously allows different pulse configurations to be generated for particular surgical applications and systems. For example, pulses having programmedrise components310 that gradually increase in power allow the lens material to be positioned more accurately. Gradual power transitions, for example, do not prematurely push the lens material away from the tip of the handpiece. In contrast, known systems using pulses having sharp minimum to maximum transitions may inadvertently push lens material away from the tip too quickly, thus complicating the surgical procedure. Accordingly, pulses that include programmed rise components can improve the positioning and cutting of lens material and the effectiveness of surgical procedures. Further, programming decay components and pulse times allows less energy to be delivered to the eye, resulting in less heating of the tissue.
• According to one embodiment, the programmed rise and/or decay component is programmed according to a linear function. In the embodiment illustrated inFIG. 3, eachpulse300 is programmed with two linear components—alinear rise component310 and alinear decay component320. Thelinear rise component310 increases from a first amplitude to a second amplitude. Anintermediate component330 extends between thelinear components310 and320 at a second amplitude. Thedecay component330 decreases from the second amplitude to a third amplitude.
• Thelinear rise component310 has alinear rise time312, thelinear decay component320 has alinear decay time322, and themaximum amplitude component330 has a maximum amplitude or active or “on”time332. Linear rise andlinear decay times312 and322 can vary depending on the maximum power level of a pulse since more time is typically required to reach higher power levels.
• In one embodiment, thelinear rise time312 can be programmed to be about 5 ms to about 500 ms. If a pulse must reach 100% power, the duration of thelinear rise time312 may be longer. However, if the pulse must reach less than 100% power, then thelinear rise time312 can be shorter, e.g. less than or about 5 ms.Linear rise time312 durations may increase with increasing power levels and can be appropriately programmed using the control console114. If necessary, the rate at which the linear component increases can be limited to protect power components, such as an amplifier.
• According to one embodiment, thelinear decay time322 can be programmed to be about 5 ms to about 500 ms. In one embodiment, theliner decay time322 is programmed using the control console114 so that power decays linearly and about 70% of the power dissipates in about 2 ms, and about 98% of the power dissipates in about 4 ms. Thelinear decay time322 may be longer than, about the same as, or shorter than thelinear rise time312. For example,FIG. 3 illustrates thedecay time322 being longer than therise time312. Thelinear decay time322 can be longer or slower than a natural decay time. The rise and decay rates may also be the same so that the pulse is symmetrical and has both programmed rise and decay components.
• The maximum amplitude or active or “on”time332 can vary with different applications. The maximum amplitude time can be about 5 ms to about 500 ms. In the illustrated embodiment, theintermediate component330 has a constant amplitude (at the second amplitude). In an alternative embodiment, the duration of the maximum amplitude time can be less than 5 ms depending on, for example, required power and resulting heat considerations. In further alternative embodiments, the amplitude may vary across theintermediate component330, e.g., increase or decrease between the first andsecond components310 and320.
• In the illustrated embodiment, therise component310 begins at a non-zero level. In an alternative embodiment, therise component310 can begin at a zero level. The initial power level may depend on the particular surgical procedure and system configuration. Similarly, thedecay component320 can end at a zero or non-zero power level.FIG. 3 illustrates the first and third amplitudes being about the same. In alternative embodiments, they can be different. For example, the third amplitude at the end of thedecay component320 can be greater than the first amplitude.
• In an alternative embodiment, the programmed rise and/or decay component can be a non-linear component. A non-linear component can be programmed according to logarithmic, exponential and other non-linear functions. For purposes of explanation, not limitation,FIG. 3 illustrates linear rise and decay components. However, one or both of the rise and decay components can be programmed with a non-linear function.
• Referring toFIG. 4, according to an alternative embodiment, apulse400 is programmed with linear rise andlinear decay components310 and320 that meet at amaximum point410 at a second amplitude rather than having anintermediate component330, as shown inFIG. 3. In the illustrated embodiment, the programmed rise anddecay times312 and322 are equal. The linear rise anddecay components310 and320 meet at a midpoint. In alternative embodiments, as discussed above with respect toFIG. 3, linear rise anddecay times312 and322 can be programmed to be about 5 ms to about 500 ms. Thus, the rise and decay times may not be equal, and themaximum point410 may not be a midpoint.
• Referring toFIGS. 5-8, in alternative embodiments, pulses having one or more linear and/or non-linear components can be combined with other pulses and pulse patterns. For purposes of explanation, not limitation,FIGS. 5-8 illustrate pulses having programmed linear components, however, one or more programmed linear components can be replaced with a programmed non-linear component.
• FIG. 5 illustrates a sequence orcombination500 of pulses having a firstrectangular pulse510, a secondrectangular pulse520, a pulse530 having a linear decay component, apulse540 having a linear rise component and apulse550 having linear rise and linear decay components, similar to the pulse shown inFIG. 4.
• FIG. 6 illustrates a sequence orcombination600 of pulses according to another embodiment that includes apulse610 having linear rise and decay components and an intermediate component, similar to the pulse shown inFIG. 3, a rectangular pulse620, a rectangular pulse630 having a longer duration than pulse620, a pulse640 having a linear decay component and apulse650 having a linear rise component.
• FIG. 7 illustrates yet a further embodiment of a sequence orcombination700 of pulses that includes apulse710 having a linear decay component, a multi-segmentrectangular pulse720 having decreasing amplitude, a pulse730 having a linear decay component, apulse740 having a linear decay component and a750 pulse having both linear rise and linear decay components, similar to the pulse shown inFIG. 4, and anotherrectangular pulse760.
• FIG. 8 illustrates a further alternative embodiment of a sequence or combination800 of pulses having the same maximum amplitude and at least one pulse having a linear component. In particular,FIG. 8 illustrates apulse810 having a linear decay component, a multi-segment rectangular pulse820 having decreasing amplitude, apulse810 having a linear decay component, apulse840 having a linear decay component, apulse850 having both linear rise and decay components, similar to the pulse shown inFIG. 4, and arectangular pulse860.
• As illustrated inFIGS. 5-8, each pulse in a packet of pulses can have an attribute that differentiates it from other pulses, e.g., based on different amplitude, duration, shape, number of programmed linear components and/or power. For example, pulse combinations can have pulses having different powers, amplitudes, shapes and durations. Further, pulse combinations can have different numbers of pulses, different numbers of rectangular and square pulses, different numbers of pulses having linear components, different numbers of pulses having one linear component, numbers of pulses having two linear components, and different numbers of pulses having two linear components and a constant amplitude component. Thus, embodiments surgeons to customize pulses to suite particular surgical procedures and phacoemulsification systems.
• As shown inFIG. 5-8, the rectangular pulses and pulses having one or more linear component, can be placed in different positions and sequences, e.g., and at the beginning or end of a pulse sequence, or somewhere in between. The order of rectangular (or other shaped pulses) and pulses having a linear component can be altered depending on the surgical application and the system used. Certain pulses may be grouped together or commingled with other types of pulses.
• For example, referring toFIG. 5,rectangular pulses510 and520 are grouped together andpulses520,530 and540 having a linear component are grouped together. In an alternative embodiment, one or more non-rectangular pulses can be between the rectangular pulses so that the rectangular pulses are commingled with different types pulses. Similarly, one or more pulses that do not include a linear component can be placed between the pulses having a programmed linear component.
• Referring toFIGS. 9-14, in alternative embodiments, pulses having a programmed linear component are included in a pattern of pulses in which each pulse has sequentially decreasing power or increasing power.FIGS. 9-11 illustrate pulse sequences in which each pulse has sequentially higher power, andFIGS. 12-14 illustrate pulse sequences in which each pulse has sequentially decreasing power.
• Referring toFIG. 9, an alternative embodiment includes a sequence orcombination900 of pulses that includespulses910,920,930,940 and950, each of which is similar to the pulses shown inFIG. 3. Each successive pulse has a higher power (P1-P5) than a prior pulse. For example,pulse930 has a power P3, which is greater than the power P2 ofpulse920.
• FIG. 10 illustrates an alternative embodiment in which a sequence orcombination1000 of pulses includespulses1010,1020,1030,1040, and1050, each of which is similar to the pulses shown inFIG. 4. Each successive pulse has a higher power than a prior pulse.
• FIG. 11 illustrates yet a further embodiment in which a sequence orcombination1100 of pulses includes pulses of various shapes and sizes, including rectangular pulses and at least one pulse having a linear component. Each successive pulse has a higher power than a prior pulse. A sequence or group of pulses having an initial low power level and subsequent increasing power levels may be useful to effectively hold and control lens material at a tip of an ultrasound handpiece, while gradually increasing power to emulsify lens material.
• Referring toFIG. 12, according to another embodiment, a sequence orcombination1200 of pulses includespulses1210,1220,1230,1240 and1250, each of which is similar to the pulse shown inFIG. 3. Each pulse includes a programmedlinear rise component310 and a programmedlinear decay component320. Each pulse has reduced power relative to a prior pulse. For example, pulse P3 has less power than pulse P2, and pulse P4 has less power than pulse P3.
• In an alternative embodiment, referring toFIG. 13, a sequence or group of pulses includespulses1310,1320,1330,1340 and1350. Each pulse is similar to the pulse shown inFIG. 4, and each pulse has reduced power relative to a prior pulse.FIG. 14 illustrates yet a further embodiment in which a sequence orcombination1400 ofpulses1410,1420,1430,1440 and1450 having reduced power over time. Thecombination1400 includes pulses having different shapes and sizes, including rectangular pulses and pulses having a linear component.
• Referring toFIGS. 15-19, alternative embodiments are directed to transforming pulses between different pulse modes in response to a controller, such as a foot pedal or foot switch. According to one embodiment, pulses are transferred between burst and pulse modes. Pulse patterns are shown relative to four foot pedal positions, which may or may not be defined by a detent or position indicator. Persons skilled in the art will appreciate that a foot pedal or switch can have other numbers of positions, and that the transitions described herein can be performed by pressing and releasing the foot pedal.
• Referring toFIG. 15, “burst” mode provides a series of periodic, fixed width,constant amplitude pulses1500 of ultrasonic power, each of which is followed by an “off”time1510. Theoff time1510 betweenpulses1500 is controlled by the surgeon's input by moving or pressing the foot pedal. In other words, in burst mode, eachpulse1500 has a fixed “on”time1520, and a variable “off”time1510, and the “off”time1510 is adjusted based on the user's manipulation of the foot pedal. Burst mode pulses can have active times of about 5 ms to about 500 ms. The spacing between bursts or the “off-time” can be about 0 ms (when the foot pedal is fully depressed and power is continuous) to about 2.5 seconds. The off-time can depend on the application and system, for example, the desired amount of cooling or heat dissipation that may be required. Burst mode pulses may be “fixed burst” mode pulses as shown inFIG. 15 or, alternatively, be “linear burst” mode pulses as shown inFIG. 16. In fixed burst mode, pressing the foot pedal decreases the off-time1510, while the amplitude of the pulses remains constant. In linear burst mode, pressing the foot pedal decreases the off-time1500 and, in addition, adjusts the amplitude. In the illustrated embodiment, pressing the foot pedal increases the amplitude. Thus, in both fixed and linear burst modes, the power “Off”time1510 can be adjusted, and the amplitude of pulses may or may not be adjusted.
• More particularly,FIGS. 15 and 16 illustrate a foot pedal in four positions. Theoff time1510 decreases when the foot pedal is initially atPosition1 and pressed further toPosition2. The number of fixed width,constant amplitude pulses1500 increases as the foot pedal is pressed. As the foot pedal is pressed fromPosition2 toPosition3, theoff time1510 eventually reaches a predetermined offtime1520, e.g., the ontime1520 or another suitable time. Pressing the foot pedal further fromposition3 toposition4 reduces theoff time1510 to zero, i.e., a 100% on-time1520 (continuous mode). A similar process is illustrated inFIG. 16, except that the pulses are linear burst mode pulses, and the amplitude of the pulses also increases as the foot pedal is moved among different positions.
• Referring toFIG. 17, in “pulse” mode, the amplitude of fixed-width pulses1700 changes according to the position of the foot pedal. In the illustrated embodiment, the amplitude increases by pressing the foot pedal.
• Referring toFIGS. 18 and 19, alternative embodiments are directed to transforming pulses between burst and pulse modes in response to movement of the foot pedal.FIG. 18 illustrates transitioning from burst mode to pulse mode. The foot pedal is pressed fromPosition1 toPosition2 to decrease theoff time1510. The off-time decreases further when the foot pedal is pressed fromPosition2 toPosition3. The number of fixed width, constant amplitude pulses in a period of time increases as the foot pedal is pressed further. As the foot pedal is pressed further, theoff time1510 eventually reaches a pre-determined value, such as the ontime1520 or another suitable value. In the illustrated embodiment, the pre-determined value is equal to the on-time1520. The pulse amplitude is then adjusted after theoff time1510 is the same as the on time1520 (or another suitable value), thereby increasing energy generated by the handpiece, and transforming pulses from burst mode to pulse mode pulses.
• Referring toFIG. 19, in an alternative embodiment, pulses are transformed from pulse mode to burst mode pulses. If the system is initially in pulse mode and the foot pedal is pressed toposition4, releasing the foot pedal initially decreases the amplitude of the pulses. After the amplitude reaches a pre-determined amplitude, releasing the foot pedal further results in adjusting the burst mode and increasing the power “Off”time1510, thereby providing fewer fixedwidth pulses1500 in a given time and less power to the ultrasonic tip113, in order to cool the tip113.
• As shown inFIGS. 18 and 19, a surgeon can advantageously switch between burst mode and pulse mode pulses by manipulating a single controller, e.g., by pressing and releasing the foot pedal. This arrangement is particularly beneficial since these transformations can be achieved without the interruptions and adjustments that are otherwise associated with changing to different pulse modes, e.g., adjusting parameters on a display screen or interface. Instead, embodiments advantageously allow continuous pulse transitions by pressing and releasing the foot pedal as part of a natural and continuous motion of the surgeon's foot, thereby simplifying the configuration and operation of surgical equipment and simplifying surgical procedures.
• Referring toFIG. 20, in a further alternative embodiment, the amount of power of each pulse can be gradually increased by utilizing a multi-step ormulti-segment pulse2000. Persons skilled in the art will appreciate that a multi-segment pulse can have two, three, four and other numbers of segments. Thus, the two-segment pulse shown inFIG. 20 is provided for purposes of illustration, not limitation.
• In the illustrated embodiment, afirst step2010 has less power than asubsequent step2020. For example, as shown inFIG. 20, afirst pulse segment2010 is at a first amplitude for a pre-determined time, followed by asecond pulse segment2020 at a second amplitude for a pre-determined time. Configuring a multi-segment pulse to provide a gradual transition from low power to higher power provides the ability to hold and emulsify lens material more accurately in contrast to abrupt transitions from low to maximum power levels such as in a typical square, which can inadvertently move lens material away from the tip during cutting of the lens material Referring toFIG. 21, in alternative embodiments, amulti-segment pulse2100 may have more than two segments of increasing amplitude. In the illustrated embodiment, a pulse has threepulse segments2110,2120 and2130. Other pulses may have four, five and other numbers of pulse segments as needed.
• The different pulses and pulse patterns described above are pulses of ultrasonic energy that can be delivered in packets to transducer elements of the handpiece. For example, as shown inFIGS. 2B and 2C, ultrasonic energy is delivered to piezoelectric elements as intermittent packets of pulses that are separated by an off period. The pulses patterns according to alternative embodiments of the invention described above are delivered to piezoelectric elements of an ultrasound handpiece during these “on” times and within these packets.
• For example,FIG. 23 illustrates packets of pulses of ultrasonic energy having sequentially increasing power, as shown inFIG. 10. As a further example,FIG. 24 illustrates packets of pulses of ultrasonic energy having sequentially decreasing power, as shown inFIG. 13. Persons skilled in the art will appreciate that a packet may have one or multiple groups of pulses, and that a packet may end at the end of a group of pulses or in the middle of a group of pulses. For example,FIGS. 22 and 23 illustrate a packet ending with the second pulse in a group of pulses. The packet may also end with the last pulse in the group of pulses. Accordingly,FIGS. 22 and 23 are provided for purposes of illustration, not limitation. Persons skilled in the art will also appreciate that the embodiments of pulses described in this specification are not required to be framed or organized in packets in order to control the ultrasound handpiece.
• Although references have been made in the foregoing description to various embodiments, persons of skilled in the art will recognize that insubstantial modifications, alterations, and substitutions can be made to the described embodiments without departing from the scope of embodiments.

Claims (25)

1. A method of generating ultrasonic energy for use with an ophthalmic surgical device, the method comprising:

generating pulses having an on-time, a first off-time, and a first amplitude, the first off-time being greater than the on-time;

reducing the first off-time of the pulses; and

increasing the amplitude of the pulses from the first amplitude to a second amplitude when the first off-time is reduced to a pre-determined second off-time.

2. The method ofclaim 1, wherein reducing the first off-time comprises reducing the first off-time in response to a controller.

3. The method ofclaim 2, wherein the controller is a foot pedal and reducing the first off-time comprises reducing the first off-time in response to movement of the foot pedal.

4. The method ofclaim 3, wherein reducing the first off-time comprises reducing the first off-time until the foot pedal reaches a pre-determined position, after which the off-time remains constant.

5. The method ofclaim 1, wherein increasing the amplitude of the pulses from the first amplitude to the second amplitude begins after the pre-determined second off-time is about the same as the on-time.

6. The method ofclaim 1, wherein increasing the amplitude comprises increasing the amplitude from the first amplitude to the second amplitude in response to a controller.

7. The method ofclaim 6, wherein the controller is a foot pedal and the first amplitude is increased in response to movement of the foot pedal.

8. The method ofclaim 7, wherein increasing the amplitude of the pulses from the first amplitude to the second amplitude begins after the foot pedal is moved to a pre-determined position.

9. The method ofclaim 1, wherein the controller is a foot pedal and continuous movement of the foot pedal initially reduces the first off-time and then increases the amplitude from the first amplitude to the second amplitude.

10. The method ofclaim 1, wherein the first off-time and the first amplitude are adjustable in response to the same controller.

11. The method ofclaim 1, wherein the on-time remains substantially constant during the steps of reducing the first off-time and increasing the first amplitude.

12. The method ofclaim 1, wherein generating pulses comprises generating rectangular pulses.

13. A method of generating ultrasonic energy for use with an ophthalmic surgical device, the method comprising:

generating burst mode pulses; and

transforming the burst mode pulses into pulse mode pulses in response to a controller.

14. The method ofclaim 13, wherein the controller is a foot pedal and transforming is performed in response to movement of the foot pedal.

15. The method ofclaim 14, wherein transforming begins after the foot pedal reaches a pre-determined position.

16. The method ofclaim 13, wherein generating burst mode pulses comprises generating rectangular pulses.

17. The method ofclaim 13, wherein generating burst mode pulses comprises generating pulses having an on-time, a first off-time and a first amplitude, and transforming the burst mode pulses comprises:

reducing the first off-time of the pulses to a second off-time in response to the controller, and when the second off-time reaches a pre-determined value,

increasing the amplitude of the pulses from the first amplitude to a second amplitude in response to the controller.

18. The method ofclaim 17, wherein the pre-determined value comprises the on-time and increasing the amplitude of the pulses from the first amplitude to the second amplitude begins after the second off-time is about the same as the on-time.

19. The method ofclaim 13, wherein the on-time remains constant during the transforming step.

20. A method of generating ultrasonic energy for use with an ophthalmic surgical device, the method comprising

generating pulse mode pulses; and

transforming the pulse mode pulses into burst mode pulses in response to a controller.

21. The method ofclaim 20, wherein the controller is a foot pedal and transforming is performed in response to movement of the foot pedal.

22. The method ofclaim 21, wherein transforming begins after the foot pedal reaches a pre-determined position.

23. The method ofclaim 20, wherein generating pulse mode pulses comprises generating rectangle pulses.

24. The method ofclaim 20, wherein generating pulse mode pulses comprises generating pulses having an on-time, a first off-time and a first amplitude, transforming the pulse mode pulses comprising reducing the amplitude from a first amplitude to a second amplitude in response to the controller, and when the second amplitude reaches a pre-determined amplitude,

increasing the first off-time to a second off-time in response to the controller.

25. The method ofclaim 24, wherein the on-time remains constant during the transforming step.

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