Abstract:
A method of irrigating a surgical site and aspirating fluid from the surgical site. The method includes directing a fluid through an aspiration conduit in a phacoemulsification hand piece using a vacuum pressure created from a pump in the hand piece interfacing with the aspiration conduit and directing an irrigation fluid through an irrigation conduit in the hand piece using a pressure created from the pump interfacing with the irrigation conduit. The method also includes increasing an irrigation fluid flow through the irrigation conduit by activating the pump in the hand piece, detecting a pressure associated with a surgical site using a sensor, and controlling intraocular pressure (IOP) by adjusting the pump speed based on the detected pressure.

Description:
BACKGROUND 
     The devices, system, and methods disclosed herein relate generally to phacoemulsification surgery, and more particularly, to a device that better regulates pressure experienced in the eye during cataract surgery. 
     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 crystalline 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 the lens. When age or disease causes the lens to become less transparent, vision deteriorates because of the diminished light which can be transmitted to the retina. This deficiency in the lens of the eye is medically known as a cataract. An accepted treatment for this condition is surgical removal of the lens and replacement of the lens function by an artificial intraocular lens (IOL). 
     In the United States, the majority of cataractous lenses are removed by a surgical technique called phacoemulsification. A typical surgical hand piece suitable for phacoemulsification procedures consists of an ultrasonically driven phacoemulsification hand piece, an attached hollow cutting needle surrounded by an irrigating sleeve, and an electronic control console. The hand piece assembly is attached to the control console by an electric cable and flexible conduit. Through the electric cable, the console varies the power level transmitted by the hand piece to the attached cutting needle. The flexible conduit supplies irrigation fluid to the surgical site and draws aspiration fluid from the eye through the hand piece assembly. 
     The operative part in a typical hand piece is a centrally located, hollow resonating bar or horn directly attached to a set of piezoelectric crystals. The crystals supply the required ultrasonic vibration needed to drive both the horn and the attached cutting needle during phacoemulsification, and are controlled by the console. The crystal/horn assembly is suspended within the hollow body or shell of the hand piece by flexible mountings. The hand piece body terminates in a reduced diameter portion or nosecone at the body&#39;s distal end. Typically, the nosecone is externally threaded to accept the hollow irrigation sleeve, which surrounds most of the length of the cutting needle. 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 needle is adjusted so that its tip projects only a predetermined amount past the open end of the irrigating sleeve. 
     During the phacoemulsification procedure, the tip of the cutting needle and the end of the irrigation sleeve are inserted into the anterior segment of the eye through a small incision in the outer tissue of the eye. The surgeon brings the tip of the cutting needle into contact with the lens of the eye, so that the vibrating tip fragments the lens. The resulting fragments are aspirated out of the eye through the interior bore of the cutting needle, along with irrigation solution provided to the eye during the procedure, and into a drain reservoir. 
     Throughout the procedure, irrigating fluid is pumped into the eye, passing between the irrigation sleeve and the cutting needle and exiting into the eye at the tip of the irrigation sleeve and/or from one or more ports, or openings, cut into the irrigation sleeve near its end. This irrigating fluid is critical, as it prevents the collapse of the eye during the removal of the emulsified lens. The irrigating fluid also protects the eye tissues from the heat generated by the vibrating of the ultrasonic cutting needle. Furthermore, the irrigating fluid suspends the fragments of the emulsified lens for aspiration from the eye. 
     A common phenomenon during a phacoemulsification procedure arises from the varying flow rates that occur throughout the surgical procedure. Varying flow rates result in varying pressure losses in the irrigation fluid path from the irrigation fluid supply to the eye, thus causing changes in pressure in the anterior chamber (also referred to as Intra-Ocular Pressure or IOP.) Higher flow rates result in greater pressure losses and lower IOP. As IOP lowers, the operating space within the eye diminishes. 
     Another common complication during the phacoemulsification process arises from a blockage, or occlusion, of the aspirating needle. As the irrigation fluid and emulsified tissue is aspirated away from the interior of the eye through the hollow cutting needle, pieces of tissue that are larger than the diameter of the needle&#39;s bore may become clogged in the needle&#39;s tip. While the tip is clogged, vacuum pressure builds up within the tip. The resulting drop in pressure in the anterior chamber in the eye when the clog is removed is known as post-occlusion surge. This post-occlusion surge can, in some cases, cause a relatively large quantity of fluid and tissue to be aspirated out of the eye too quickly, potentially causing the eye to collapse and/or causing the lens capsule to be torn. 
     Various techniques have been designed to reduce this surge. However, there remains a need for improved phacoemulsification devices that reduce post-occlusion surge as well as maintain a stable IOP throughout varying flow conditions. Eliminating the need for complex active irrigation systems and reducing the number of required devices is also needed. The present disclosure addresses one or more deficiencies in the prior art. 
     SUMMARY 
     In an exemplary aspect, the present disclosure is directed a phacoemulsification hand piece. The hand piece includes a body having a distal end and a proximal end, an ultrasonic tip disposed at the distal end of the body and configured to aspirate an aspiration fluid from a surgical site, and a sleeve disposed at the distal end of the body configured to irrigate the surgical site with an irrigation fluid. The hand piece also includes a removable cartridge disposed in the body and in fluid communication with the ultrasonic tip and the sleeve, wherein the cartridge comprises an aspiration conduit configured to contain the aspiration fluid and an irrigation conduit configured to contain the irrigation fluid. The hand piece also includes a pump disposed within the body and interfacing with the aspiration conduit and with the irrigation conduit, such that upon activation of the pump, the irrigation fluid within the irrigation conduit flows in a direction towards the sleeve and away from the proximal end, and the aspiration fluid within the aspiration conduit flows in a direction away from the tip and towards the proximal end. 
     In an aspect, the hand piece also includes a valve disposed within the body and configured to interface with the aspiration conduit, the valve configured to control a flow rate of aspiration fluid within the aspiration conduit. 
     In another exemplary aspect, the present disclosure is directed to a method of irrigating a surgical site and aspirating fluid from the surgical site. The method includes directing a fluid through an aspiration conduit in a phacoemulsification hand piece using a vacuum pressure created from a pump in the hand piece interfacing with the aspiration conduit and directing an irrigation fluid through an irrigation conduit in the hand piece using a pressure created from the pump interfacing with the irrigation conduit. The method also includes increasing an irrigation fluid flow through the irrigation conduit by activating the pump in the hand piece, detecting a pressure associated with a surgical site using a sensor, and controlling intraocular pressure (IOP) by adjusting the state of an aspiration valve based on the detected pressure. 
     In an aspect, the method includes controlling IOP by adjusting a pump speed based on the pressure. 
     In another exemplary aspect, the present disclosure is directed to an aspiration and irrigation system for irrigating the eye and aspirating fluid from the eye during an ocular surgery. The system includes a phacoemulsification hand piece comprising a graspable body having a distal end and a proximal end, an aspiration conduit configured to transport an aspiration fluid away from a surgical site, and an irrigation conduit configured to transport an irrigation fluid towards the surgical site. The system also includes a pump disposed within the hand piece, wherein at least a portion of the pump interfaces with the aspiration conduit and the irrigation conduit, such that upon activation of the pump, the irrigation fluid within the irrigation conduit flows in a direction towards the surgical site, and the aspiration fluid within the aspiration conduit flows in a direction away from the surgical site. The system also includes a valve disposed within the hand piece configured to interface with the aspiration conduit, the valve configured to control a flow rate of aspiration fluid within the aspiration conduit. The system also includes a sensor detecting pressure representative of a surgical site pressure and a controller in communication with the pump, the valve, and the sensor, wherein the controller is configured to control the operation of the pump and the valve based on information from the sensor, and wherein the controller is configured to change intraocular pressure (IOP) at the surgical site. 
     In an aspect, the controller is configured to change IOP by adjusting the pump speed or by adjusting the state of the valve or both. 
     It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory in nature and are intended to provide an understanding of the present disclosure without limiting the scope of the present disclosure. In that regard, additional aspects, features, and advantages of the present disclosure will be apparent to one skilled in the art from the following detailed description. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The accompanying drawings illustrate embodiments of the devices and methods disclosed herein and together with the description, serve to explain the principles of the present disclosure. 
         FIG. 1  is an illustration of an exemplary phacoemulsification surgical console according to an embodiment consistent with the principles of the present disclosure. 
         FIG. 2  is a block diagram of the phacoemulsification console of  FIG. 1  showing various subsystems including a fluidics subsystem that drives aspiration and irrigation according to an embodiment consistent with the principles of the present disclosure. 
         FIG. 3  is a block diagram of a part of the fluidics subsystem of  FIG. 2  with a phacoemulsification hand piece having an integrated pump according to an embodiment consistent with the principles of the present disclosure. 
         FIG. 4  is flow chart illustration of a method of operating the phacoemulsification hand piece of  FIG. 3 , according to an embodiment consistent with the principles of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     For the purposes of promoting an understanding of the principles of the present disclosure, reference will now be made to the embodiments illustrated in the drawings, and specific language will be used to describe the same. It will nevertheless be understood that no limitation of the scope of the disclosure is intended. Any alterations and further modifications to the described devices, instruments, methods, and any further application of the principles of the present disclosure are fully contemplated as would normally occur to one skilled in the art to which the disclosure relates. In particular, it is fully contemplated that the features, components, and/or steps described with respect to one embodiment may be combined with the features, components, and/or steps described with respect to other embodiments of the present disclosure. For the sake of brevity, however, the numerous iterations of these combinations will not be described separately. For simplicity, in some instances the same reference numbers are used throughout the drawings to refer to the same or like parts. 
     The present disclosure relates generally to devices, systems, and methods for phacoemulsification procedures. Maintaining the IOP within a predetermined range during phacoemulsification may be important to the success of the procedure. The flow of irrigation fluid into the surgical site and the flow of aspiration fluid out of the surgical site are two significant factors affecting the IOP. Early detection and correction of any changes to the irrigation fluid flow or aspiration fluid flow greatly improves the stability of the IOP. 
     The devices, system, and methods disclosed herein include a hand piece with an integrated aspiration and irrigation pump and an aspiration valve designed to quickly change the aspiration flow and irrigation flow. In the embodiment disclosed herein, the use of one pump located in the hand piece to control both the irrigation flow and aspiration flow allows for quick adjustments to flow while maintaining a graspable hand piece body size. In some embodiments, the hand piece includes a sensor detecting IOP information at the surgical site. This allows for the early detection of IOP changes. 
       FIG. 1  illustrates an exemplary emulsification surgical console, generally designated  100 .  FIG. 2  is a block diagram of the console  100  showing various subsystems that operate to perform a phacoemulsification procedure. The console  100  includes a base housing  102  with a computer system  103  and an associated display screen  104  showing data relating to system operation and performance during a phacoemulsification surgical procedure. The console  100  also includes at least a part of a number of subsystems that are used together to perform an emulsification surgical procedure. Some of these subsystems include components or elements that are separable from or not disposed on the console  100 . For example, the subsystems include a foot pedal subsystem  106  that includes, for example, a foot pedal  108 , a fluidics subsystem  110  including a hand piece  112  with an integrated aspiration and irrigation pump, an ultrasonic generator subsystem  116  that provides an ultrasonic oscillation to a cutting needle of the hand piece  112 , and a pneumatic vitrectomy cutter subsystem  120  including a vitrectomy hand piece  122  (not shown in  FIG. 1 ). These subsystems may overlap and cooperate to perform various aspects of the procedure. 
       FIG. 3  is a block diagram schematically illustrating a part of the fluidics subsystem  110  according to an exemplary embodiment. The fluidics subsystem  110  includes an irrigation system  335 , an aspiration system  365 , and the hand piece  112 . In  FIG. 3 , hand piece  112  comprises a graspable body  305  having a distal end denoted by number  310  and a proximal end denoted by number  315 . A cutting tip  320  and an irrigation sleeve  325  extend from the distal end  310  and are in fluid communication with a surgical site, such as an eye during a phacoemulsification procedure. In  FIG. 3 , the cutting up  320  and the irrigation sleeve  325  are shown separate for ease of understanding, however, these may be coaxial or otherwise arranged. The hand piece  112  includes portions of the irrigation system  335  and portions of the aspiration system  365 . In addition, the hand piece  112  includes a pump  360  and a sensor  392  associated with the aspiration system  365 . In some exemplary embodiments, the sensor  392  may be located along the aspiration path  375  or located near the distal end  310  and in fluid communication with the surgical site. In some embodiments, the sensor  392  may be located within the surgical site and in communication with a controller forming a part of the fluidics subsystem  110 , as described below. In some embodiments, the sensor  392  detects a pressure at the surgical site or a pressure associated with the surgical site. In this exemplary embodiment, the hand piece  112  also includes an aspiration valve  390 , which is shown associated with the aspiration system  365 . 
     The irrigation system  335  includes an irrigation conduit  340  that forms an irrigation path  345  that is in fluid communication with the sleeve  325  and an irrigation fluid supply  350 . Irrigation fluid  355  flows from the irrigation fluid supply  350 , through the irrigation conduit  340  and through the sleeve  325  into the surgical site. The irrigation fluid supply  350  may be located, for example, on an intravenous pole at a fixed or adjustable height or otherwise disposed about the system. In one embodiment, the irrigation conduit  340  and the irrigation fluid supply  350  are not in contact with the base housing  102 , therefore active irrigation is eliminated. The irrigation conduit  340  may be a flexible tubing. In the exemplary embodiment shown, the pump  360  interfaces with the flexible irrigation conduit  340 . In some embodiments, the irrigation system  335  includes an optional irrigation sensor  342  that may be used to detect fluid characteristics of the irrigation fluid in the irrigation conduit  340 . In one embodiment and as shown in  FIG. 3 , the optional irrigation sensor  342  is located along the irrigation path  345  between the driver  400  and the distal end  310 . In another embodiment (not shown), the optional irrigation sensor  342  is located along the irrigation path  345  between the driver  400  and the proximal end  315 . In one embodiment, the optional irrigation sensor  342  is a pressure transducer configured to detect pressure within the irrigation conduit  340 . The pressure transducer may be configured to detect pressure upstream from the pump  360  and the detected pressure may be correlated to a flow rate. In embodiments where the pressure transducer is disposed to detect pressure downstream from the pump  360 , the detected pressure may be correlated to a flow rate or may be correlated to pressure within the surgical site or may be correlated to IOP. In another embodiment, the optional irrigation sensor  342  is a flow sensor that directly measures flow in the irrigation conduit  340 . 
     The aspiration system  365  includes an aspiration conduit  370  that forms an aspiration path  375  that is in fluid communication with the tip  320  and a drain reservoir  380 . In some embodiments, the aspiration conduit  370  is a flexible tubing. Aspiration fluid  385  flows away from the surgical site, through the tip  320  and collects in the drain reservoir  380 . The aspiration system  365  also comprises the aspiration valve  390 . In some embodiments, the aspiration valve  390  is a variable controlled valve. In some embodiments, the aspiration valve  390  is a peizotronic valve. In the embodiment shown, the aspiration valve  390  is located between the pump  360  and the proximal end  315 . In the exemplary embodiment shown, the pump  360  interfaces with the flexible aspiration conduit  370 . Aspiration fluid  385  generally comprises irrigation fluid  355  that has been in contact with the surgical site, and other matter, such as an eye lens, that is to be removed from the surgical site. 
     In  FIG. 3 , the pump  360  simultaneously interfaces with both the irrigation conduit  340  and the aspiration conduit  370 . The pump  360  comprises a motor  395  and a driver  400 . In some embodiments, the pump  360  is a peristaltic pump. In one embodiment, the driver  400  has a spiral structure that presses against the flexible aspiration conduit  370  and the flexible irrigation conduit  340 . In this manner, a screw-type or scroll-type aspiration pump is implemented with the motor  395 , the driver  400 , the aspiration conduit  370 , and the irrigation conduit  340 . The irrigation conduit  340  is disposed so that the movement of the driver  400  causes the irrigation fluid  355  to flow away from the irrigation fluid supply  350  and towards the surgical site while it simultaneously causes the aspiration fluid  385  to flow away from the surgical site and towards the drain reservoir  380 . The motor  395  is coupled to the driver  400  and serves to rotate the driver  400 . The motor  395  can be controlled to control the movement of the driver  400  as more clearly described below. The motor  395  is typically a DC motor but can be any type of motor or driver suitable for rotating the driver  400 . While the pump  360  is described as a screw-type peristaltic pump, other types of pumps may also be used. 
     In  FIG. 3 , the fluidics subsystem  110  may also include a controller  405 . In some embodiments, the controller  405  is disposed on the console  100 . The controller  405  is in communication with the sensor  392  and the optional irrigation sensor  342  and is configured to receive IOP information from the sensor  392  or the optional irrigation sensor  342  or both. The controller  405  may include a processor and memory that may include an executable program for operating the aspiration valve  390 , for operating the pump  360 , and or detecting information received from the sensors  392 ,  342 . The controller  405  may receive inputs from an operator or may include pre-stored optimum targets for the irrigation flow or the aspiration flow or both. These target and received inputs may be a single value or a range of values. In one embodiment, the controller  405  is a PID controller configured to control the aspiration valve  390  to mitigate pressure deviations. 
     In one example, the controller  405  may include one or more pre-established optimum flow thresholds establishing desired fluid flow in the aspiration conduit  370 , or the irrigation conduit  340 , or both. The controller  405  may include an optimum irrigation flow threshold that is a function of an irrigation pressure or irrigation fluid flow rate. The controller  405  may include an optimum aspiration flow threshold that is a function of an aspiration pressure or aspiration fluid flow rate. Similar thresholds may be included for a pressure setting and a vacuum setting. These thresholds may be input by an operator or may be preset and stored during manufacturing. 
     The controller  405  is in communication with the pump  360  and is configured to control the operation of the pump  360 . In operation, the motor  395  rotates the driver  400 . The controller  405  controls the operation of the motor  395 . In this manner, the driver  400  may be rotated at any desired speed to produce any desired aspiration flow and irrigation flow. When rotated, the driver  400  draws the aspiration fluid  385  through the aspiration conduit  370 , and draws the irrigation fluid  355  through the irrigation conduit  340  towards the surgical site. The controller  405  uses the pressure information received from the sensor  392  or the optional irrigation sensor  342  or both to determine whether the speed of the pump  360  should be increased or decreased to maintain or regulate IOP. 
     The controller  405  is in communication with the aspiration valve  390  and is configured to control the state of the aspiration valve  390 , meaning the controller controls the valve to move to a more open position, a fully open position, a more closed position, or fully closed position. In some embodiments, the flow of the aspiration fluid  385  is controlled by the state of the aspiration valve  390 . The more open the aspiration valve  390 , the higher the flow of the aspiration fluid  385  within the aspiration conduit  370 . The less open the aspiration valve  390 , the lower the flow of the aspiration fluid  385  within the aspiration conduit  370 . The controller  405  uses the pressure or flow information received from the sensor  392  to determine whether the state of the aspiration valve  390  should be adjusted (increased or decreased). The controller  405  may be configured to control the IOP using any of a plurality of different or overlapping methods. Some embodiments employ the pump  360  in the hand piece to maintain a desired pressure or a desired flow to the eye. In one embodiment, the controller  405  is configured to maintain IOP by operating the pump at pre-established speed settings that correspond to particular flow rates through the irrigation conduit  340 . Accordingly, to increase or decrease the flow rates to a desired target flow rate, the controller  405  controls the pump speed. In other embodiments, the controller  405  receives detected information from the optional irrigation sensor  342 , and based on this information, the controller  405  is a responsive system that increases or decreases the pump speed to achieve the desired flow rate. 
     Other embodiments employ the valve  390  in the hand piece to maintain a desired pressure or a desired flow to the eye. In these embodiments, with the pump speed held constant, the controller  405  may control the valve  390  to increase or decrease the flow through the aspiration conduit  370 . In some embodiments, the controller  405  operates the valve  390  to maintain aspiration fluid flow within a desired or target flow rate. This may be done by detecting a pressure or the flow rate in the aspiration conduit  370  with the sensor  392 , and controlling the valve  390  to increase or decrease the flow rate through the valve  390 . In some embodiments, the controller  405  operates the valve  390  based on valve position, where the flow rate is known based on the position on the valve  390 . Accordingly for any given flow rate, the system may maintain the flow rate within a target range by setting the valve to a state that corresponds with the desired flow rate. 
     Yet other embodiments employ both the pump  360  and the valve  390  to achieve the desired flow rates, and likewise, the corresponding desired IOP. For example, a faster response may be achieved by simultaneously controlling both the pump speed and the valve state to increase or decrease flow in a manner to maintain a desired IOP. 
     In one embodiment, the body  305  includes an opening configured to receive a removable hand piece cartridge  406 . The removable cartridge  406  comprises a portion of the irrigation system  335  and the aspiration system  365 , with the portions of the irrigation system  335  and aspiration systems  365  being in fluid communication with the tip  320  and the sleeve  325 . The use of a removable hand piece cartridge  406  eliminates the need for fluidic cassettes that are generally attached to or within the base housing  102  of the console  100 . The removable cartridge  406  may be snapped into place to selectively engage with the pump. In some embodiments, the removable cartridge is for a one-time use. 
     In one embodiment, the length of aspiration conduit and irrigation conduit between the pump  360  and the surgical site is minimal (on the order of inches or centimeters). In addition, this length of aspiration conduit and irrigation conduit between the pump and the surgical site may be non-compliant (i.e., it can be rigid). This is represented in  FIG. 3  by the length of conduit  407 . Having a small length of non-compliant conduit  407  between the pump  360  and the surgical site may relieve post-occlusion surge associated with prior art systems. 
     The cross-sectional areas of the irrigation and aspiration conduits  340 ,  370  may be selected to provide a desired flow rate. In some embodiments, a cross sectional area of the irrigation conduit  340  and a cross sectional area of the aspiration conduit  370  are the same. In other embodiments, the cross-sectional areas are different. In one embodiment, the cross sectional area of the irrigation conduit  340  may be larger than the cross sectional area of the aspiration conduit  370  in order to achieve an irrigation fluid flow that is greater than the aspiration fluid flow, thereby ensuring that the irrigation fluid flow is greater than the aspiration fluid flow. Due to the irrigation conduit  340  and aspiration conduit  370  both interfacing with the driver  400  of the motor  395 , differing the cross sectional areas allows for the same driver rotation to produce a variety of irrigation fluid flow to aspiration fluid flow ratios. 
     In the exemplary embodiment shown in  FIG. 3 , the pressure sensor  392  is located along the aspiration path  375  between the pump  360  and the distal end  310 . In this manner, the sensor  392  can accurately read the pressure conditions in the aspiration conduit  370  very close to the surgical site. Detecting pressure conditions close to the surgical site results in early detection of occlusion breaks, and therefore, allowing for early response to prevention of occlusion surges. In some embodiments (not shown), the pressure sensor  392  is located along the aspiration path  375  between the pump  360  and the proximal end  315 . 
     In another embodiment, the irrigation system  335  includes an optional shunt line and irrigation valve  396  (shown in dashed lines), which may be a variable controlled valve. In one embodiment, the valve is a peizotronic valve. However other valves also may be used. The valve  396  may be used to bleed irrigation fluid downstream from the pump to the aspiration line downstream of the aspiration valve  390 . The valve  396  also may be controlled by the controller and may be adjusted to affect fluid flow through the irrigation line. For example, the valve  396  may be opened to permit fluid flow to continue through the irrigation line when the aspiration valve is closed to affect IOP. This may also reduce the likelihood of an IOP spike when the aspiration valve  390  is controlled. 
       FIG. 4  illustrates an exemplary method of operating the fluidics subsystem  110 . The method is generally referred to by the reference number  410 . Using the method  410 , the fluidics subsystem  110  may detect pressure deviations in the system, such as those that may occur as a result of an occlusion surge, and may quickly act to counter the effects of the occlusion surge. For example, the fluidics subsystem  110  may use the information from the sensor  392  to detect clogged tips due to changes in pressure, as an indicator of the IOP in the eye. Upon detecting a clog (based on the pressure readings or IOP information from the sensor  392 ), aspiration and irrigation flows can be adjusted using the pump  360  and the aspiration valve  390 , to reduce the effects of a post-occlusion surge. The continuous detection of the IOP information by the sensor  392  may result in a more consistent and predictable phacoemulsification procedure by reducing the effects of pressure deviations that occur with post-occlusion surges. That is, by immediately responding to the deviations in pressure. 
     Referring to  FIG. 4 , at a step  420 , the surgeon sets a target IOP on the console and/or a desired flow. The controller  405  activates the pump  360  to cause the irrigation fluid  355  to flow through the irrigation conduit  340  and the aspiration fluid  385  to flow through the aspiration conduit  370 . 
     At a step  425 , the controller  405  receives information from the aspiration sensor  392  and determines whether the IOP is at the set IOP of within a range of the set IOP. From this, the system may calculate, or may also directly measure, the flow. If the IOP is within the desired range, the system continues to measure IOP as indicated at step  430 . It should be noted that the optimum irrigation flow may be either a specific target value or may be a range of values. If the IOP is outside the desired range, then the system adjusts the pump valve setting to alter the flow at a step  435 , thereby directly influencing the IOP. The pump valve adjustment may be done to either increase the flow or to decrease the flow based on the measurement taken. In some embodiments, the system also adjusts the setting on the optional irrigation valve  396  to permit at least a portion of the irrigation fluid to bypass the IOP to reduce the likelihood of an IOP spike. 
     In conventional phacoemulsification systems, the pump is located within the base housing  102 . A relatively long length of flexible conduit (six feet or more) is located between an aspiration and irrigation pump and the eye. This relatively long length of flexible conduit has a lot of compliance—it can stretch in response to changes in vacuum pressure. This compliance can result in surges as previously described. By incorporating the pump that interfaces with both the irrigation conduit and the aspiration conduit in the hand piece  112  (and placing it very close to the eye) and having a very short length of non-compliant conduit  407  between the pump  360  and the eye, the effects of these surges can be reduced or eliminated, thus resulting in a more consistent and predictable surgery. The system disclosed herein, with the hand piece pump  360  that drives both the irrigation and the aspiration may decrease conduit compliance, decrease pump control delay times, may decrease irrigation resistance to flow, and/or may decrease other delays that might result from using a pressure transducer far down stream in a fluidics cassette. Additionally, because the pump  360  interfaces with the irrigation conduit  340  and causes the irrigation fluid  385  to flow through the irrigation path  375 , active irrigation or the pumping of irrigation fluid from the base housing  102 , is no longer needed. In addition, some components are eliminated or replaced by this system, such as a fluidics cassette and an active irrigation system. 
     In one embodiment however, a single-use, removable hand piece cartridge of the hand piece  112  may replace the fluidics cassette which, in conventional systems, is temporarily placed in the base housing  102 . Instead, the irrigation conduit may be directly connected from the hand piece  112  to the irrigation fluid supply  350 , which can be located at a fixed bottle height. 
     Persons of ordinary skill in the art will appreciate that the embodiments encompassed by the present disclosure are not limited to the particular exemplary embodiments described above. In that regard, although illustrative embodiments have been shown and described, a wide range of modification, change, and substitution is contemplated in the foregoing disclosure. It is understood that such variations may be made to the foregoing without departing from the scope of the present disclosure. Accordingly, it is appropriate that the appended claims be construed broadly and in a manner consistent with the present disclosure.