Pulse manipulation for controlling a phacoemulsification surgical system

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

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, a method of generating energy for use with an ophthalmic surgical device includes generating a group of pulses having at least one pulse that includes a programmed substantially linear component and at least one pulse having an attribute that is different from the pulse having the programmed substantially linear component. According to another embodiment, a method of generating energy for use with an ophthalmic surgical device includes generating a group of pulses, the group of pulses. The group of pulses includes at least one pulse that includes a programmed substantially linear component; and at least one pulse that does not include a programmed substantially linear component. Each pulse differs from at least one other pulse in the group in at least one manner. In accordance with yet a further embodiment, a method of generating energy for use with an ophthalmic surgical device includes generating a group of pulses including one or more rectangular pulses and one or more pulses having a programmed substantially linear component.

In various embodiments, the group of pulses, such as two to ten pulses, can have having sequentially different power, e.g., sequentially decreasing and sequentially increasing power. The pulses in the group can have the same or different amplitudes. The pulses in the group can have different on-times. The pulses can have the same or different shapes. A pulse in the group can be a rectangular pulse or a triangular pulse. The triangular pulse can have one or two programmed linear components, e.g., programmed linear rise and/or decay components. A pulse can also include a programmed non-linear decay component. A controller, such as a foot pedal, can be used to change the amplitude of the group of pulses.

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 2illustrate exemplary surgical systems.

FIG. 1illustrates one suitable system and represents the INFINITI® Vision System available from Alcon Laboratories, Inc., 6201 South Freeway, Q-148, Fort Worth, Tex. 76134.FIG. 2Aillustrates an exemplary control system100that can be used with this system.

The control system100is used to operate an ultrasound handpiece112and includes a control console114, which has a control module or CPU116, an aspiration, vacuum or peristaltic pump118, a handpiece power supply120, an irrigation flow or pressure sensor122(such as in the Infiniti® system) and a valve124. Various ultrasound handpieces112and 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 CPU116may be any suitable microprocessor, micro-controller, computer or digital logic controller. The pump118may be a peristaltic, a diaphragm, a Venturi or other suitable pump. The power supply120may be any suitable ultrasonic driver. The irrigation pressure sensor122may be various commercially available sensors. The valve124may 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 sensor122is connected to the handpiece112and the infusion fluid source126through irrigation lines130,132and134. The irrigation pressure sensor122measures the flow or pressure of irrigation fluid from the source126to the handpiece112and supplies this information to the CPU116through the cable136. The irrigation fluid flow data may be used by the CPU116to control the operating parameters of the console114using software commands. For example, the CPU116may, through a cable140, vary the output of the power supply120being sent to the handpiece112and the tip113though a power cable142. The CPU116may also use data supplied by the irrigation pressure sensor122to vary the operation of the pump118and/or valves through a cable144. The pump118aspirates fluid from the handpiece112through a line146and into a collection container128through line148. The CPU116may also use data supplied by the irrigation pressure sensor122and the applied output of power supply120to provide audible tones to the user. Additional details concerning such surgical systems can be found in U.S. Pat. No. 6,179,808 (Boukhny, 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 console114can be programmed to control and manipulate pulses that are delivered to the handpiece112and, 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 and decay components310and312of each pulse300can be programmed separately from a natural rise and natural decay. For example rise and decay components310and312can 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 and decay components310and312and rise and decay times312and322provides advantageously allows different pulse configurations to be generated for particular surgical applications and systems. For example, pulses having programmed rise components310that 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, each pulse300is programmed with two linear components—a linear rise component310and a linear decay component320. The linear rise component310increases from a first amplitude to a second amplitude. An intermediate component330extends between the linear components310and320at a second amplitude. The decay component330decreases from the second amplitude to a third amplitude.

The linear rise component310has a linear rise time312, the linear decay component320has a linear decay time322, and the maximum amplitude component330has a maximum amplitude or active or “on” time332. Linear rise and linear decay times312and322can vary depending on the maximum power level of a pulse since more time is typically required to reach higher power levels.

In one embodiment, the linear rise time312can be programmed to be about 5 ms to about 500 ms. If a pulse must reach 100% power, the duration of the linear rise time312may be longer. However, if the pulse must reach less than 100% power, then the linear rise time312can be shorter, e.g. less than or about 5 ms. Linear rise time312durations 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, the linear decay time322can be programmed to be about 5 ms to about 500 ms. In one embodiment, the liner decay time322is programmed using the control console114so 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. The linear decay time322may be longer than, about the same as, or shorter than the linear rise time312. For example,FIG. 3illustrates the decay time322being longer than the rise time312. The linear decay time322can 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” time332can vary with different applications. The maximum amplitude time can be about 5 ms to about 500 ms. In the illustrated embodiment, the intermediate component330has 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 the intermediate component330, e.g., increase or decrease between the first and second components310and320.

In the illustrated embodiment, the rise component310begins at a non-zero level. In an alternative embodiment, the rise component310can begin at a zero level. The initial power level may depend on the particular surgical procedure and system configuration. Similarly, the decay component320can end at a zero or non-zero power level.FIG. 3illustrates 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 the decay component320can 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. 3illustrates 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, a pulse400is programmed with linear rise and linear decay components310and320that meet at a maximum point410at a second amplitude rather than having an intermediate component330, as shown inFIG. 3. In the illustrated embodiment, the programmed rise and decay times312and322are equal. The linear rise and decay components310and320meet at a midpoint. In alternative embodiments, as discussed above with respect toFIG. 3, linear rise and decay times312and322can be programmed to be about 5 ms to about 500 ms. Thus, the rise and decay times may not be equal, and the maximum point410may 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. 5-8illustrate pulses having programmed linear components, however, one or more programmed linear components can be replaced with a programmed non-linear component.

FIG. 5illustrates a sequence or combination500of pulses having a first rectangular pulse510, a second rectangular pulse520, a pulse530having a linear decay component, a pulse540having a linear rise component and a pulse550having linear rise and linear decay components, similar to the pulse shown inFIG. 4.

FIG. 6illustrates a sequence or combination600of pulses according to another embodiment that includes a pulse610having linear rise and decay components and an intermediate component, similar to the pulse shown inFIG. 3, a rectangular pulse620, a rectangular pulse630having a longer duration than pulse620, a pulse640having a linear decay component and a pulse650having a linear rise component.

FIG. 7illustrates yet a further embodiment of a sequence or combination700of pulses that includes a pulse710having a linear decay component, a multi-segment rectangular pulse720having decreasing amplitude, a pulse730having a linear decay component, a pulse740having a linear decay component and a750pulse having both linear rise and linear decay components, similar to the pulse shown inFIG. 4, and another rectangular pulse760.

FIG. 8illustrates a further alternative embodiment of a sequence or combination800of pulses having the same maximum amplitude and at least one pulse having a linear component. In particular,FIG. 8illustrates a pulse810having a linear decay component, a multi-segment rectangular pulse820having decreasing amplitude, a pulse810having a linear decay component, a pulse840having a linear decay component, a pulse850having both linear rise and decay components, similar to the pulse shown inFIG. 4, and a rectangular 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 pulses510and520are grouped together and pulses520,530and540having 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. 9-11illustrate pulse sequences in which each pulse has sequentially higher power, andFIGS. 12-14illustrate pulse sequences in which each pulse has sequentially decreasing power.

Referring toFIG. 9, an alternative embodiment includes a sequence or combination900of pulses that includes pulses910,920,930,940and950, 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, pulse930has a power P3, which is greater than the power P2of pulse920.

FIG. 10illustrates an alternative embodiment in which a sequence or combination1000of pulses includes pulses1010,1020,1030,1040, and1050, each of which is similar to the pulses shown inFIG. 4. Each successive pulse has a higher power than a prior pulse.

FIG. 11illustrates yet a further embodiment in which a sequence or combination1100of 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 or combination1200of pulses includes pulses1210,1220,1230,1240and1250, each of which is similar to the pulse shown inFIG. 3. Each pulse includes a programmed linear rise component310and a programmed linear decay component320. Each pulse has reduced power relative to a prior pulse. For example, pulse P3has less power than pulse P2, and pulse P4has less power than pulse P3.

In an alternative embodiment, referring toFIG. 13, a sequence or group of pulses includes pulses1310,1320,1330,1340and1350. Each pulse is similar to the pulse shown inFIG. 4, and each pulse has reduced power relative to a prior pulse.FIG. 14illustrates yet a further embodiment in which a sequence or combination1400of pulses1410,1420,1430,1440and1450having reduced power over time. The combination1400includes 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 pulses1500of ultrasonic power, each of which is followed by an “off” time1510. The off time1510between pulses1500is controlled by the surgeon's input by moving or pressing the foot pedal. In other words, in burst mode, each pulse1500has a fixed “on” time1520, and a variable “off” time1510, and the “off” time1510is 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. 15or, 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-time1500and, 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” time1510can be adjusted, and the amplitude of pulses may or may not be adjusted.

More particularly,FIGS. 15 and 16illustrate a foot pedal in four positions. The off time1510decreases when the foot pedal is initially at Position1and pressed further to Position2. The number of fixed width, constant amplitude pulses1500increases as the foot pedal is pressed. As the foot pedal is pressed from Position2to Position3, the off time1510eventually reaches a predetermined off time1520, e.g., the on time1520or another suitable time. Pressing the foot pedal further from position3to position4reduces the off time1510to 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 pulses1700changes 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. 18illustrates transitioning from burst mode to pulse mode. The foot pedal is pressed from Position1to Position2to decrease the off time1510. The off-time decreases further when the foot pedal is pressed from Position2to Position3. 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, the off time1510eventually reaches a pre-determined value, such as the on time1520or another suitable value. In the illustrated embodiment, the pre-determined value is equal to the on-time1520. The pulse amplitude is then adjusted after the off time1510is 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 to position4, releasing the foot pedal initially decreases the amplitude of the pulses. After the amplitude reaches a predetermined amplitude, releasing the foot pedal further results in adjusting the burst mode and increasing the power “Off” time1510, thereby providing fewer fixed width pulses1500in 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 or multi-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. 20is provided for purposes of illustration, not limitation.

In the illustrated embodiment, a first step2010has less power than a subsequent step2020. For example, as shown inFIG. 20, a first pulse segment2010is at a first amplitude for a predetermined time, followed by a second pulse segment2020at a second amplitude for a predetermined 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, a multi-segment pulse2100may have more than two segments of increasing amplitude. In the illustrated embodiment, a pulse has three pulse segments2110,2120and2130. 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. 23illustrates packets of pulses of ultrasonic energy having sequentially increasing power, as shown inFIG. 10. As a further example,FIG. 24illustrates 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 23illustrate 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 23are 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.