Abstract:
Disclosed herein is an apparatus for insertion in an eye of a patient for aspirating material from the eye in the treatment of an ocular condition, the apparatus comprising a needle disposed at a distal end of the apparatus, an aspiration channel extending from a distal aperture of the needle to a proximal end of the apparatus, and an irrigation sleeve coaxially disposed about the needle. The aspiration channel comprises a proximal portion having a first diameter, a bypass portion having a second diameter and at least one bypass port, and a distal portion having a third diameter. The second diameter is larger than the first diameter. The irrigation sleeve and the needle form an annular irrigation passageway therebetween. The bypass port is shaped and configured to establish fluid communication between the irrigation passageway and the aspiration channel.

Description:
BACKGROUND 
     Visually impairing cataract, or clouding of the lens, is the leading cause of preventable blindness in the world. An accepted treatment for cataracts is surgical removal of the affected lens and replacement with an artificial intraocular lens (“IOL”). Cataract extractions are among the most commonly performed operations in the world. 
       FIG. 1  is a diagram of an eye  10  showing some of the anatomical structures related to the surgical removal of cataracts and the implantation of IOLs. The eye  10  comprises a lens  12 , an optically clear cornea  14 , and an iris  16 . A lens capsule  18 , located behind the iris  16  of the eye  10 , contains the lens  12 , which is seated between an anterior capsule segment or anterior capsule  20  and a posterior capsular segment or posterior capsule  22 . The anterior capsule  20  and the posterior capsule  22  meet at an equatorial region of the lens capsule  18 . The eye  10  also comprises an anterior chamber  24  located in front of the iris  16  and a posterior chamber  26  located between the iris  16  and the lens capsule  18 . 
     The eye  10  functions to provide vision by transmitting light through the cornea  14 , and focusing the image by way of the lens  10  onto a retina  25 . The quality of the focused image depends on many factors including the size and shape of the eye, and the transparency of the cornea  14  and the lens  10 . When age or disease causes the lens to become less transparent or opacified, vision deteriorates because of the diminished light which may be transmitted to the retina  25 . The cataract is this deficiency in the lens  10 . 
     A common technique of cataract surgery known as extracapsular cataract extraction (“ECCE”) involves the creation of an incision  30  near the outer edge of the cornea  14  and an opening in the anterior capsule  20  (i.e., an anterior capsulotomy) through which the opacified lens  12  is removed. The lens  12  can be removed by various known methods including phacoemulsification, in which ultrasonic energy is applied to the lens  12  to break it into small pieces that are promptly aspirated from the lens capsule  18 . 
     A common complication of phacoemulsification procedures 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 emulsified tissue may become at least momentarily lodged in the aspirating lumen. Such blockages may cause undesirable pressure changes in the eye and/or the handpiece. For example, when the aspiration lumen is clogged, vacuum pressure may rapidly increase within the lumen. After the clog is removed, the resulting drop in anterior chamber pressure is known as post-occlusion surge, which can cause a 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  18  to be torn. 
     Various equipment designs and methods have been derived in order to minimize the problems introduced by a blocked aspiration lumen during a phacoemulsification procedure or other cataract removal procedure. However, there remains a need for devices, systems, and methods to more effectively prevent or minimize these blockages. The devices, systems, and methods disclosed herein overcome one or more of the deficiencies of the prior art. 
     SUMMARY 
     In one exemplary aspect, the present disclosure is directed to an apparatus for insertion in an eye of a patient for aspirating material from the eye in the treatment of an ocular condition. In one aspect, the apparatus comprises a needle disposed at a distal end of the apparatus with an aspiration channel extending from the distal aperture of the needle to a proximal end of the apparatus. In one aspect, the aspiration channel comprises a proximal portion having a first diameter, a bypass portion having a second diameter, and a distal portion having a third diameter, wherein the second diameter is larger than the first diameter. In one aspect, the apparatus includes an irrigation sleeve coaxially disposed about the needle, with the irrigation sleeve and the needle forming an annular irrigation passageway therebetween. In one aspect, the apparatus includes at least one bypass port formed within the bypass portion of the aspiration channel. In one aspect, the at least one bypass port is shaped and configured to establish fluid communication between the irrigation passageway and the aspiration channel. 
     In another exemplary aspect, the present disclosure is directed to an apparatus for insertion in an eye of a patient for aspirating material from the eye in the treatment of an ocular condition. In one aspect, the apparatus comprises an aspiration channel extending from a distal end to a proximal end of the apparatus. In one aspect, the aspiration channel comprises a proximal portion having a first diameter, a bypass portion having a second diameter, and a distal portion having a third diameter. In one aspect, the distal portion is in fluid communication with the distal aperture of the needle. In one aspect, the second diameter is larger than the first diameter. In one aspect, the apparatus comprises an irrigation sleeve coaxially disposed about the aspiration channel, with the irrigation sleeve and the aspiration channel forming an annular irrigation passageway therebetween. In one aspect, the apparatus comprises at least one bypass port formed within the bypass portion of the aspiration channel, wherein the at least one bypass port is shaped and configured to establish fluid communication between the irrigation passageway and the aspiration channel. In one aspect, the apparatus comprises a sealing element disposed on the irrigation sleeve adjacent the irrigation passageway, with the sealing element being shaped and configured to selectively seat against the at least one bypass port and block fluid flow through the at least one bypass port with the application of force on the sealing element. 
     In another exemplary aspect, the present disclosure is directed to a method for controlling vacuum pressures within an aspiration handpiece for insertion within an eye of a patient. In one aspect, the method includes positioning a distal tip of the aspiration handpiece within the eye, with the distal tip in fluid communication with an aspiration channel extending from the distal tip to a proximal end of the handpiece. In one aspect, the aspiration channel includes a distal portion having a first diameter and a bypass portion having a second diameter that is larger than the first diameter and including at least one bypass port. In one aspect, the method includes providing irrigation fluid to the eye through an irrigation sleeve coaxially disposed about the aspiration channel, with the irrigation sleeve and the needle forming an annular irrigation passageway therebetween. In one aspect, the method includes allowing irrigation fluid to pass from the irrigation passageway into the aspiration lumen through the at least one bypass port. In one aspect, the method includes providing a vacuum pressure within the aspiration channel to aspirate fluid and tissue from the eye through the distal tip into the aspiration channel. 
     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 a diagram of a cross-sectional view of an eye. 
         FIG. 2  illustrates a perspective view of an exemplary instrument positioned within the eye according to one embodiment consistent with the principles of the present disclosure. 
         FIG. 3  is a diagram of the components in the fluid path of an exemplary phacoemulsification system according to one embodiment consistent with the principles of the present disclosure. 
         FIG. 4 a    illustrates a partially cross-sectional view of a distal portion of an exemplary instrument according to one embodiment consistent with the principles of the present disclosure. 
         FIG. 4 b    illustrates a diagram of a distal portion of an exemplary instrument according to one embodiment consistent with the principles of the present disclosure. 
         FIG. 4 c    illustrates a diagram of an exemplary instrument according to one embodiment consistent with the principles of the present disclosure. 
         FIG. 5  illustrates a cross-sectional view of the instrument shown in  FIG. 4 a    along lines  5 - 5  in the area of an exemplary bypass portion according to one embodiment consistent with the principles of the present disclosure. 
         FIG. 6  illustrates a cross-sectional view of an exemplary instrument according to another embodiment consistent with the principles of the present disclosure. 
         FIG. 7  illustrates a cross-sectional view of an exemplary bypass portion of the instrument shown in  FIG. 6  according to one embodiment consistent with the principles of the present disclosure. 
         FIG. 8  illustrates a cross-sectional view of an exemplary instrument according to another embodiment consistent with the principles of the present disclosure. 
         FIG. 9  illustrates a cross-sectional view of an exemplary bypass portion of the instrument shown in  FIG. 8  according to one embodiment consistent with the principles of the present disclosure. 
         FIG. 10  illustrates a detailed view of the exemplary bypass portion shown in  FIG. 8  where the bypass port is in an open condition according to one embodiment consistent with the principles of the present disclosure. 
         FIG. 11  illustrates a detailed view of the exemplary bypass portion shown in  FIG. 8  where the bypass port is in a closed condition according to one 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 use in treating medical conditions, including ophthalmic conditions such as cataract. In some instances, embodiments of the present disclosure comprise surgical instruments designed to reduce the occurrence of blockages of the aspiration lumen of a surgical handpiece during cataract extraction and minimizing the negative effects of such blockages. In some exemplary embodiments disclosed herein, the instrument includes at least one bypass port disposed within an area of increased inner diameter along the aspiration path. Having the bypass ports disposed within an area of increased diameter along the path of aspiration of the instrument may reduce the risk of occluding a bypass port, which consequently reduces the risk of post-occlusion surge. In some exemplary embodiments disclosed herein, the surgical instrument is configured to allow the user to selectively affect the vacuum level within the handpiece by temporarily blocking at least one bypass port with the aspiration path by manually manipulating an irrigation sleeve surrounding the aspiration path. The embodiments disclosed herein allow the user to actively control the aspiration vacuum at the tip of the instrument by manipulating the irrigation sleeve at a specific aspiration flow rate to either (1) reduce the bypass surface area and immediately increase the tip vacuum, or (2) revert to the original bypass surface area to immediately decrease the tip vacuum. 
       FIG. 2  illustrates a common technique of cataract surgery known as extracapsular cataract extraction (“ECCE”), which involves the creation of an incision  30  near the outer edge of the cornea  14  and an opening in the anterior capsule  20  (i.e., an anterior capsulotomy) through which the opacified lens  12  is removed. The lens  12  can be removed by various known methods including phacoemulsification, in which ultrasonic energy is applied to the lens  12  to break it into small pieces that are promptly aspirated from the lens capsule  18 . 
       FIG. 2  depicts an aspiration instrument  100  for removing the lens  12  by emulsification and aspiration through the incision  30  in accordance with the present disclosure. The instrument  100  may be any of a variety of handpieces configured for aspiration of material from the interior of the eye  10 , including, by way of non-limiting example, a phacoemulsification handpiece. A typical surgical handpiece suitable for phacoemulsification procedures consists of an ultrasonically driven phacoemulsification handpiece, an attached hollow cutting needle surrounded by an irrigating sleeve, and an electronic control console. The instrument  100  includes an aspiration tip  105 , a hollow cutting needle  110 , and an irrigation sleeve  115 . The irrigation sleeve  115  surrounds the cutting needle  110  and is disposed co-axially about a longitudinal axis of the cutting needle  110 . The instrument  100  may be attached to a control console  120  by an electric cable  125  and flexible tubing  130 . Through the electric cable  125 , the console  120  may vary the power level transmitted by the instrument  100  to the cutting needle  110 . In some embodiments, the control console  120  includes a display, a guided user interface, and/or other accessory devices (not shown). The flexible tubing  130  supplies irrigation fluid to the surgical site through the irrigation sleeve  115  and draws aspiration fluid from the eye  10  through aspiration tip  105  of the instrument  100 . 
     During the phacoemulsification procedure, the aspiration tip  105  of the cutting needle  110  and the end of the irrigation sleeve  115  are inserted into the anterior capsule  20  through the incision near the outer edge of the cornea  14 . The surgeon brings the cutting needle  110  into contact with the lens  12  so that the vibrating tip emulsifies or fragments the lens. By way of non-limiting example, various forms of energy that may be coupled to the cutting needle  110  include ultrasonic energy, laser energy, thermal energy, and electrical energy. The resulting fragments are aspirated out of the eye  10  through an interior lumen  135  (not shown in  FIG. 2 ) of the cutting needle  110  along with the irrigation solution provided to the eye  10  during the procedure. Following removal of the opacified lens  12 , an artificial IOL is typically implanted within the lens capsule  18  through the opening in the anterior capsule  20  to mimic the transparency and refractive function of a healthy lens. 
       FIG. 3  is a diagram of the components in the fluid path of an exemplary phacoemulsification system  200  according to one embodiment consistent with the principles of the present disclosure.  FIG. 3  depicts the fluid path through the eye  10  during a phacoemulsification procedure. The components include an irrigation fluid source  202 , an irrigation pressure sensor  205 , an irrigation valve  210 , an irrigation line  215 , the instrument  100 , an aspiration line  225 , an aspiration pressure sensor  230 , a vent valve or bypass port  235 , a pump  240 , a reservoir  245 , and a drain bag  250 . In some embodiments, the irrigation line  215  and the aspiration line  225  may be the same as the flexible tubing  130  described above in relation to  FIG. 2 . The irrigation line  215  provides irrigation fluid to the eye  10  during the procedure. The pump  240  operates to draw fluid and emulsified tissue (e.g., lens tissue) from the eye and through the aspiration line  225  during the procedure. The aspiration pressure sensor  230  measures the vacuum pressure within the aspiration line  225 , and may be able to detect an increase in vacuum pressure associated with an occlusion inside the aspiration line  225  (and/or a decrease in vacuum pressure associated with occlusion break). The aspirated fluid and tissue passes through the reservoir  245  into the drain bag  250 . 
     Some embodiments actively monitor sensed data from the aspiration pressure sensor and actively adjust the operation of the instrument  100  (e.g., the vacuum level of the pump  240  and/or the flow rate) in response to the sensed aspiration pressure. Some embodiments may lack an aspiration pressure sensor  230 . Some embodiments may lack active pressure measurement monitoring altogether. Various instruments  100  may be capable of producing vacuum pressures of over 700 mm Hg in milliseconds. However, very high vacuum pressures may be undesirable in certain surgical applications, including, by way of non-limiting example, capsule polishing and cortex removal. In such embodiments, the aspiration vacuum levels may need to be controlled via adjusting the flow rate to mitigate potential risks associated with sharply elevated pressures within the aspiration line  225 . In some embodiments, the instrument  100  may utilize the vent valve  235  to vent or relieve the vacuum pressure within the aspiration line  225  created by the pump  240 . 
     When the irrigation fluid exits the irrigation fluid source  202 , the fluid travels through the irrigation line  215  and into the eye  10 . The irrigation pressure sensor  205  measures the pressure of the irrigation fluid in the irrigation line  215 , and may be capable of detecting an increase in pressure associated with an occlusion within the aspiration line  225  (and/or a decrease in vacuum pressure associated with occlusion break). The irrigation pressure sensor  205  may comprise any of a variety of fluid pressure sensors and may be located anywhere in the irrigation fluid path (i.e., anywhere between the irrigation fluid source  202  and the eye  10 ). The irrigation valve  210  may provide on/off control of the irrigation. Other embodiments may lack an irrigation pressure sensor  205  and/or an irrigation valve  210 . 
       FIG. 4 a    illustrates a distal portion of a handpiece  400 , which may be the same as the instrument  100  described above with reference to  FIGS. 2 and 3 . The handpiece  400  includes a cutting needle  410 , an irrigation sleeve  415 , and a body  416 . The cutting needle  410  and the irrigation sleeve  415  may be the same as the cutting needle  110  and the irrigation sleeve  115  described above with relation to  FIGS. 2 and 3 . As mentioned above in relation to  FIG. 2 , the handpiece  400  is placed in the eye  10  during a cataract removal procedure, such as, by way of non-limiting example, a phacoemulsification procedure. In some embodiments, the cutting needle  410  may be ultrasonically vibrated to break up or emulsify the diseased lens. The irrigation fluid flows from the irrigation line  215  through the irrigation passageway  416  to exit into the eye through the irrigation ports  418  in the direction of arrows  440 . 
     The irrigation sleeve  415  concentrically surrounds the cutting needle  410  to define an annular irrigation passageway  417  therebetween. The irrigation sleeve  415  includes at least one irrigation port  418  disposed near a distal tip or distal aperture  422  of the cutting needle  410 . For example, in the pictured embodiment, the irrigation sleeve  415  includes two irrigation ports  418 . 
     In the pictured embodiment, the irrigation sleeve  415  is detachably coupled to the cutting needle  410 . The irrigation sleeve  415  may be detachably coupled to the cutting needle  410  by any of a variety of means, including, by way of non-limiting example, a threaded engagement, a snap-fit engagement, a frictional engagement, and/or any other mechanism for temporarily connecting the irrigation sleeve  415  to the handpiece  400 . The cutting needle  410  may be likewise coupled to the body  418  of the handpiece  400  by any of a variety of detachable or temporary means, including, by way of non-limiting example, a threaded engagement, a snap-fit engagement, a frictional engagement, and/or any other mechanism for temporarily connecting the cutting needle  410  to the handpiece  400 . 
     An aspiration channel  420  extends through the cutting needle  410  and the body  416  along a longitudinal axis LA of the handpiece  400 . The aspiration channel  420  defines an aspiration lumen  421  running therethough, which may be fluidically coupled to the aspiration line  225  to enable deposition of aspirated material into the reservoir  245  and/or the drain bag  250  (described above in relation to  FIG. 3 ). A distal tip  422  of the cutting needle  410  comprises an opening in fluid communication with the aspiration lumen  421 . Fluid and emulsified tissue may be aspirated from the eye through the distal tip  422  into the aspiration lumen  421  of the cutting needle  410 . 
     In the pictured embodiment, the aspiration channel  420  includes a distal portion  424 , a bypass portion  425 , and a proximal portion  426 . The bypass portion  425  is shaped and configured as a passageway between the distal portion  424  and the proximal portion  426  of the aspiration channel  420 . The proximal portion runs through the body  416  of the handpiece  400 , and the distal portion  424  runs through the cutting needle  410 . 
     The bypass portion  425  may be formed as part of the cutting needle  410 , as a separate coupler or attachment, or as part of the body  416  of the handpiece  400 . In the pictured embodiment in  FIG. 4 a   , the bypass portion forms a proximal extension of the cutting needle  410 . In other embodiments, as shown in  FIG. 4 b   , the bypass portion  425 ′ of an aspiration lumen  420 ′ of an instrument  400 ′ may comprise a separate coupler  431  that can be removably coupled to the body  416 ′ and the cutting needle  410 ′. In other embodiments, as shown in  FIG. 4 c   , the bypass portion  425 ″ of an aspiration lumen  420 ″ of an instrument  400 ″ may form a distal extension of the body  416 ″ coupled to a needle  410 ″. 
     The aspiration channel  420  extends through various component parts of the handpiece  400 , and includes an inner or luminal diameter that varies along the length of the aspiration channel  420 . The inner diameter varies between the distal portion  424 , the bypass portion  425 , and the proximal portion  426 . The distal portion  424  includes an inner diameter D1, the bypass portion  425  includes an inner diameter D2, and the proximal portion includes an inner diameter D3. In the pictured embodiment, the inner diameter D2 of the bypass portion  425  is greater than the inner diameter D1 of the distal portion  424  and the inner diameter D3 of the proximal portion  426 . In some other embodiments, the inner diameter D2 of the bypass portion  425  may be substantially the same as the inner diameter D3 of the proximal portion  426 . 
       FIG. 5  illustrates a cross-sectional view of the instrument  400  along line 5-5 in  FIG. 4 a    at the bypass portion  425 . As shown in  FIG. 5 , the bypass portion  425  comprises a housing  427  having an inner surface  428  and an outer surface  429 . The inner surface  428  is in contact with the aspirated fluid and tissue material within the aspiration lumen  421  of the aspiration channel  420 . The outer surface  429  is in contact with the irrigation passageway  417 . The housing  427  includes a wall thickness T1 extending from the inner surface  428  to the outer surface  429 . In some embodiments, the thickness T1 is constant throughout the entire bypass portion  425 . In other embodiments, the thickness T1 varies either longitudinally along the length of the bypass portion  425  or at discrete areas such as adjacent a bypass port  430 , which is described below with reference to  FIGS. 4 and 5 . 
     As shown in  FIGS. 4 and 5 , the bypass portion  425  includes at least one bypass port  430 . The bypass port  430  is an aperture in the housing  427  of the bypass portion  425  that fluidically connects the aspiration lumen  421  with the irrigation passageway  417  in the area of the bypass portion  425 . The bypass port  430  includes a sidewall thickness T2, which may be substantially the same as the wall thickness T1 of the bypass portion  425 . In other embodiments, the thickness T2 of the sidewall of the bypass port  430  may be less than the thickness of the remainder of the housing  427  of the bypass portion. In some embodiments, as described further below with reference to  FIGS. 6-11 , the user may control the vacuum pressure within the aspiration channel  420  by selectively opening and closing the bypass port to  430  selectively decrease and increase, respectively, the vacuum pressure while maintaining a substantially constant aspiration flow rate. 
     As shown in  FIG. 5 , the bypass ports  430  include an inner diameter Db that spans the width of the apertures in the housing  427 . In some embodiments, the diameter Db ranges from 0.005-0.020 inches. For example, in one embodiment, the diameter Db may measure 0.006 in. These measurements are provided by way of example only, and are not intended to be limiting. Other diameters are contemplated. Although the bypass ports  430  in the pictured embodiment have a circular shape, the bypass ports  430  may be formed in any of a variety of shapes, including without limitation, ovoid, rectangular, crescent, slit-like, and rhomboid shapes. 
     In the pictured embodiment, the bypass portion  425  includes two bypass ports  430 . It should be understood that a varying number of bypass ports  430  can be used and that the bypass ports  430  may be arranged on the bypass portion  425  in any of a variety of patterns. For example, such bypass ports  430  can be staggered with respect to each other rather than being formed directly opposite one another. The bypass ports  430  may be positioned at the same or different longitudinal positions along the length of the bypass portion  425 . For example, at least one bypass port  430  may be disposed farther from the distal tip  422  of the cutting needle  410  than at least one other bypass port  430 . 
     As mentioned above, very high vacuum pressures may be undesirable in certain surgical applications, including, by way of non-limiting example, capsule polishing and cortex removal. In such surgical applications, the instrument  100  may utilize the bypass port  430  (in combination with relatively low aspiration rates) to relieve the vacuum pressure within the aspiration line  225  created by the pump  240  and to maintain the vacuum levels at the desired low level. Bypass ports in traditional aspiration lines may be occluded by aspirated tissue as it travels past the bypass port within the aspiration channel, which results in a rapid increase in vacuum pressure within the aspiration channel. In contrast, the bypass ports  430  described herein are disposed within the bypass portion  425 , which is an area of increased inner diameter along the aspiration channel  420 . By increasing the inner diameter of the portion of the aspiration channel  420  (i.e., the bypass portion  425 ) carrying the bypass ports  430  relative to the remainder of the aspiration channel  420 , the risk of occlusion is minimized. In particular, the relatively large inner diameter D2 of the bypass portion  425  reduces the risk of inadvertent occlusion of the bypass ports  430  with aspirated material. This, in turn, reduces the risk of unintended and/or uncontrolled rises in vacuum levels during aspiration. In addition, at low flow rates and higher bypass volumes or cross-sectional areas, the tip vacuum level will decrease significantly upon the occurrence of a tip occlusion. In applications involving polishing of the lens capsule, for example, this provides added protection to the lens capsule because the propensity of the tip for inadvertently “grabbing” the capsule is reduced. Thus, having the bypass ports  430  disposed within the larger bypass portion  425  allows the user more control over vacuum pressure variations in surgical instruments that traditionally exhibited extremely rapid changes in vacuum levels within the aspiration channel  420  during unintentional occlusion of bypass ports. 
     The aspiration channels  420  and, in particular, the bypass portions  425  described herein can be made from a variety of suitable materials without departing from the scope of the present disclosure. By way of non-limiting example, the instrument tips described herein can be made from titanium, stainless steel, alloys thereof, or any other suitable material. 
       FIG. 6  illustrates a cross-sectional view of an exemplary handpiece  600  according to another embodiment consistent with the principles of the present disclosure. In some embodiments, the handpiece  600  may be the same as the instrument  100  described above with reference to  FIGS. 2 and 3 . The handpiece  600  includes a cutting needle  610 , an irrigation sleeve  615 , and a body  616 . The cutting needle  610  and the irrigation sleeve  615  may be the same as the cutting needle  110  and the irrigation sleeve  115  described above with relation to  FIGS. 2 and 3 . 
     The irrigation sleeve  615  concentrically surrounds the cutting needle  610  to define an annular irrigation passageway  617  therebetween. The irrigation sleeve  615  includes at least one inlet port  614  shaped and configured to allow the influx of irrigation solution into the irrigation passageway  617 . The irrigation sleeve  615  includes at least one irrigation port  618  disposed near a distal tip  619  of the cutting needle  610 . For example, in the pictured embodiment, the irrigation sleeve  615  includes two irrigation ports  618 . The irrigation ports  618  are shaped and configured to allow the efflux of irrigation fluid into the eye during surgical procedure. The irrigation sleeve includes a sealing element  650  that is shaped and configured to selectively contact and seal against the bypass port  630 . The sealing element  650  is described in further detail below with reference to  FIGS. 6 and 7 . 
     In the pictured embodiment, the irrigation sleeve  615  is detachably coupled to the cutting needle  610 . The irrigation sleeve  615  may be detachably coupled to the cutting needle  610  be any of a variety of means, including, by way of non-limiting example, a threaded engagement, a snap-fit engagement, a frictional engagement, and/or any other mechanism for temporarily connecting the irrigation sleeve  615  to the handpiece  600 . The cutting needle  610  may be likewise coupled to the body  618  of the handpiece  600  by any of a variety of detachable or temporary means, including, by way of non-limiting example, a threaded engagement, a snap-fit engagement, a frictional engagement, and/or any other mechanism for temporarily connecting the cutting needle  610  to the handpiece  600 . 
     An aspiration channel  620  extends through the cutting needle  610  and the body  616  along a longitudinal axis LA of the handpiece  600 . The aspiration channel  620  defines an aspiration lumen  821  running therethough, which may be fluidically coupled to the aspiration line  225  to enable deposition of aspirated material into the reservoir  245  and/or the drain bag  250  (described above in relation to  FIG. 3 ). The distal tip  619  of the cutting needle  610  comprises an opening in fluid communication with the aspiration lumen  621 . The aspiration channel  620  extends through various component parts of the handpiece  600 , and may include an inner or luminal diameter that varies along the length of the aspiration channel  620 . 
     In the pictured embodiment, the aspiration channel  620  includes a distal portion  624 , a bypass portion  625 , and a proximal portion  626 . The bypass portion  625  is shaped and configured as a passageway between the distal portion  624  and the proximal portion  626  of the aspiration channel  620 . The proximal portion  626  runs through the body  616  of the handpiece  400 , and the distal portion  624  runs through the cutting needle  610 . The bypass portion  625  may be formed as part of the cutting needle  610 , as a separate coupler or attachment, or as part of the body  616  of the handpiece  600 . In the pictured embodiment, the bypass portion forms a proximal extension of the cutting needle  610 . In other embodiments, the bypass portion  625  may comprise a separate coupler that can be removably coupled to the body  616  and the cutting needle  610 . In other embodiments, the bypass portion  625  may form a distal extension of the body  616 . 
     In some embodiments, the bypass portion  625  is substantially similar to the bypass portion  425  described above in relation to  FIGS. 4 and 5 , except for the differences described herein. The inner diameter may vary between the distal portion  624 , the bypass portion  625 , and the proximal portion  626  as described in relation to the handpiece  400 . In other embodiments, an inner diameter D4 of the bypass portion  625  may be substantially the same as an inner diameter D3 of the distal portion  624  and/or an inner diameter D5 of the proximal portion  626 . For example, in the pictured embodiment in  FIG. 6 , the inner diameter D4 of the bypass portion  625  is larger than the inner diameter D3 of the distal portion  624 , but is substantially the same as the inner diameter D5 of the proximal portion  626 . 
     As shown in  FIG. 6 , the bypass portion  625  comprises a housing  627  having an inner surface  628  and an outer surface  629 . The inner surface  628  is in contact with the aspirated fluid and tissue material within the aspiration lumen  621  of the aspiration channel  620 . The outer surface  629  is in contact with the irrigation passageway  617 . 
       FIG. 7  illustrates a cross-sectional view of the bypass portion  625  along the line 7-7 according to one embodiment consistent with the principles of the present disclosure. As shown in  FIGS. 6 and 7 , the bypass portion  625  includes at least one bypass port  630 . In the pictured embodiment, the bypass portion  625  includes two bypass ports,  630   a  and  630   b . Other embodiments may include only the bypass port  630   a . In the pictured embodiment, the bypass ports  630   a  and  630   b  are disposed opposite each other at a substantially identical longitudinal distance along the aspiration channel  620  from the distal tip  619 . In the pictured embodiment, the bypass ports  630   a  and  630   b  are sized identically. In other embodiments, the bypass port  630   a  may be sized to have a larger cross-sectional area than the bypass port  630   b , thereby allowing for a greater reduction in flow rate when the bypass port  630   a  is blocked to increase tip vacuum. 
     It should be understood that a varying number of bypass ports  630  can be used and that the bypass ports  630  may be arranged on the bypass portion  625  in any of a variety of patterns. For example, the bypass ports  630   a ,  630   b  can be staggered with respect to each other rather than being formed directly opposite one another as shown. The bypass ports  630   a ,  630   b  may be positioned at the same or different longitudinal positions along the length of the bypass portion  625 . For example, the bypass port  630   a  may be disposed farther from the distal tip  619  of the cutting needle  610  than the bypass port  630   b . Although the bypass ports  630   a ,  630   b  in the pictured embodiment have a circular shape, the bypass ports  630   a ,  630   b  may be formed in any of a variety of shapes, including without limitation, ovoid, rectangular, crescent, slit-like, and rhomboid shapes. 
     The housing  627  includes a wall thickness T3 extending from the inner surface  628  to the outer surface  629 . In some embodiments, the thickness T3 varies either longitudinally along the length of the bypass portion  625  or at discrete areas such as adjacent a bypass port  630 . For example, in the pictured embodiment, the housing  627  is shaped to receive at least a portion of the sealing element  650  and the thickness T3 decreases in the area adjacent the bypass ports  630   a ,  630   b  to accommodate the sealing element  650 . In other embodiments, the thickness T3 is constant throughout the entire bypass portion  625 . 
     The bypass ports  630   a ,  630   b  are apertures in the housing  627  of the bypass portion  625  that fluidically connect the aspiration lumen  621  with the irrigation passageway  617  in the area of the bypass portion  625 . As shown in  FIGS. 6 and 7 , the bypass ports  630   a ,  630   b  include a sidewall thickness T4, which is less than the thickness T3 of the housing  627  in other areas of the bypass portion  625 . In other embodiments, the thickness T4 of the sidewall of the bypass ports  630   a ,  630   b  may be substantially the same as the wall thickness T3 of the bypass portion  625 . 
     As mentioned above, the irrigation sleeve  615  includes the sealing element  650 , which is disposed on the irrigation sleeve  615  so as to overlie at least one of the bypass ports  630 . As shown in  FIG. 7 , the sealing element  650  is disposed on the irrigation sleeve  615  such that the sealing element  650  and the bypass port  630   a  are coaxially aligned about a central axis CA extending through the bypass port  630   a . In the pictured embodiment in  FIGS. 6 and 7 , the sealing element  650  comprises a pushbutton-like structure that may be depressed onto the bypass port  630   a  to reduce or eliminate flow through the bypass port  630   a.    
     The sealing element  650  includes an exterior side  655  and an opposing interior side  660 . The exterior side  655  is substantially continuous with an exterior surface  665  of the irrigation sleeve  615 . The exterior side  655  is shaped and configured to facilitate a user&#39;s manual depression of the sealing element  650 . The interior side  660  is substantially continuous with an interior surface  670  of the irrigation sleeve  615 . The interior side  660  is shaped and configured to block flow through the bypass port  630   a  when the sealing element  650  is depressed inward to contact the outer surface  629  of the housing  627  of the bypass portion  625 . In some embodiments, the interior side  660  may be deformable and shape under pressure to seat at least partially within the bypass port  630   a.    
     The sealing element  650  includes a central section  675  and a peripheral section  680 , which circumferentially surrounds the central section  675 . When the sealing element  650  is depressed, the central section  675  moves toward the housing  627  of the bypass portion  625 . When the interior side  660  of the sealing element  650  contacts the outer surface  629  of the housing  627 , the sealing element  650  blocks the ingress and/or egress of fluid and tissue through the bypass port  630   a . The sealing element  650  contacts the irrigation sleeve  615  at the peripheral section  680 . In the pictured embodiment, the central section  675  is substantially thicker than the peripheral section  680 . In the pictured embodiment, the peripheral section  680  is curved to facilitate the inward and outward movement of the sealing element  650 . In other embodiments, the peripheral section  680  is substantially flat. 
     In some embodiments, the sealing element  650  may be formed as an integral part of the irrigation sleeve  615 . In other embodiments, the sealing element  650  may be formed as a separate component of the handpiece  600  that is fixedly attached the irrigation sleeve  615  by the peripheral section  680  by welding, overmolding, adhesive, or any other suitable means for fixedly attaching the sealing element  650  to the irrigation sleeve  615  in a fluid-tight fashion. 
     In some embodiments, the sealing element  650  is formed of silicone. In other embodiments, the sealing element  650  may be constructed of any of a variety of suitable materials, including by way of non-limiting example, silicon, nitrile rubber, and polyisoprene. 
     It should be understood that a varying number of sealing elements  650  can be used to correspond to the number of bypass ports  630  in the handpiece  600 . For example, other embodiments may include another sealing element  650   b  (not shown) on the irrigation sleeve  615  shaped and configured to block flow through the bypass port  630   b . The bypass ports  630  and their corresponding sealing elements  650  may be arranged relative to the bypass portion  625  in any of a variety of patterns. As mentioned above, some embodiments may lack bypass port  630   b.    
     The aspiration channels  620  and, in particular, the bypass portions  625  described herein can be made from a variety of suitable materials without departing from the scope of the present disclosure. By way of non-limiting example, the instrument tips described herein can be made from titanium, stainless steel, alloys thereof, or any other suitable material. 
     While using handpieces capable of producing a rapid increase in aspiration vacuum to 700 mmHg or more within a short time (e.g., 20 to 30 milliseconds), the user may control the vacuum pressure by utilizing the bypass ports (e.g., bypass ports  630   a ,  630   b ) and varying the overall aspiration flow rate. In general, the resulting tip vacuum pressure produced at a specific aspiration flow rate is highly repeatable and predictable. In some applications, however, very high vacuum pressures may be desirable for very brief periods of time, including, by way of non-limiting example, during an occlusion of the distal tip  619  of the aspiration channel  620  to clear the occlusion. In some applications, rapid increases in vacuum pressure may improve the purchase of lens material when the distal tip  619  contacts the lens material. A user employing the handpiece  600  may rapidly increase the tip vacuum pressure within the aspiration lumen  620  without necessarily changing the aspiration flow rate. 
     In particular, the user may rapidly increase the tip vacuum pressure within the aspiration lumen  620  by depressing the sealing element  650  until the sealing element  650  contacts the bypass port  630   a  to selectively modify the amount of bypass available in the system. In particular, when the interior side  660  of the central section  675  of the sealing element  650  contacts the outer surface  629  of the housing  627  overlying the bypass port  630   a , the sealing element  650  blocks the flow through the bypass port  630   a . When the sealing element  650  contacts the bypass port  630   a , the vacuum pressure within the aspiration lumen  621  rapidly increases, which allows the user to grab and aspirate unwanted tissue material through the distal tip  619  into the aspiration lumen  621 . By selectively blocking the bypass port  630   a  and decreasing the total cross-sectional area of the bypass ports, higher tip vacuums can be attained quickly in order to capture and aspirate unwanted tissue while the handpiece  600  operates at a constant aspiration flow rate. 
     When the user releases or reduces manual pressure on the sealing element  650 , the sealing element  650  will lift away from the bypass port  630   a  and return to a resting or neutral position. When the bypass port  630   a  is unblocked, the tip vacuum will immediately decrease. Accordingly, if tissue (e.g., the lens capsule) is inadvertently “grabbed” by the distal tip  619 , the user can immediately release or decrease pressure on the sealing element  650  to reduce the tip vacuum and release the tissue from the distal tip  619 . Therefore, the handpiece  600  enables the user to temporarily create a high tip vacuum without necessarily changing the overall aspiration flow rate. This allows the tip vacuum at a specific flow rate to remain repeatable and predictable. In the alternative, the user may reduce the aspiration flow rate to reduce the tip vacuum and release the tissue from the distal tip  619 . In addition, the handpiece  600  allows the user more real-time control over aspiration vacuum pressures during ophthalmic surgeries, for example in response to occlusions within the aspiration lumen  621 . 
     In some embodiments, the handpiece  600  may be connected to a control console  120  (as shown in  FIG. 2 ) having display capabilities. In such embodiments, the control console may be configured to display the range of tip vacuum pressures that is possible using the handpiece  600 . For example, at a known aspiration flow rate, the control console  120  may display both the tip vacuum pressure possible when the sealing element  650  is blocking the bypass port  630   a  and the tip vacuum pressure possible when the sealing element  650  is not blocking the bypass port  630   a . Thus, the maximum and minimum tip vacuum levels could be displayed on the control console  120  as a direct function of the aspiration flow rate. In some embodiments, the control console  120  may display the real-time tip vacuum pressure. 
       FIG. 8  illustrates a cross-sectional view of a distal portion of an exemplary handpiece  800  according to another embodiment consistent with the principles of the present disclosure. In some embodiments, the handpiece  800  may be the same as the instrument  100  described above with reference to  FIGS. 2 and 3 . The handpiece  800  includes a cutting needle  810 , an irrigation sleeve  815 , and a body  816 . The cutting needle  810  and the irrigation sleeve  815  may be the same as the cutting needle  110  and the irrigation sleeve  115  described above with relation to  FIGS. 2 and 3 . The cutting needle  815 , the body  816 , and the irrigation sleeve  815  are substantially similar to the cutting needle  610  and the body  616  described above in relation to  FIGS. 6 and 7  except for the differences described herein. 
     The irrigation sleeve  815  concentrically surrounds the cutting needle  810  to define an annular irrigation passageway  817  therebetween. The irrigation sleeve  815  includes at least one irrigation port  818  disposed near a distal tip  819  of the cutting needle  810 . For example, in the pictured embodiment, the irrigation sleeve  815  includes two irrigation ports  818 . The irrigation ports  818  are shaped and configured to allow the efflux of irrigation fluid into the eye during surgical procedure. 
     The irrigation sleeve  815  includes a fluid-tight chamber  880 . The fluid-tight chamber  880  comprises an annular space formed entirely within the irrigation sleeve  815 . In addition, the irrigation sleeve  815  includes a sealing element  850  that is shaped and configured to selectively contact and seal against a bypass port  830   a . The sealing element  850 , the bypass port  830   a , and the chamber  880  are described in further detail below with reference to both  FIGS. 8 and 9 . 
     An aspiration channel  820  extends through the cutting needle  810  and the body  816  along a longitudinal axis LA of the handpiece  400 . The aspiration channel  820  defines an aspiration lumen  821  running therethough, which may be fluidically coupled to the aspiration line  225  to enable deposition of aspirated material into the reservoir  245  and/or the drain bag  250  (described above in relation to  FIG. 3 ). The distal tip  819  of the cutting needle  810  comprises an opening in fluid communication with the aspiration lumen  821 . The aspiration channel  820  extends through various component parts of the handpiece  800 , and may include an inner or luminal diameter that varies along the length of the aspiration channel  820 . 
     In the pictured embodiment, the aspiration channel  820  includes a distal portion  824 , a bypass portion  825 , and a proximal portion  826 . The bypass portion  825  is shaped and configured as a passageway between the distal portion  824  and the proximal portion  826  of the aspiration channel  820 . The proximal portion  826  runs through the body  816  of the handpiece  800 , and the distal portion  824  runs through the cutting needle  810 . The bypass portion  825  may be formed as part of the cutting needle  810 , as a separate coupler or attachment, or as part of the body  816  of the handpiece  400 . In the pictured embodiment, the bypass portion forms distal extension of the body  816 . In other embodiments, the bypass portion  825  may comprise a separate coupler that can be removably coupled to the body  816  and the cutting needle  810 . In other embodiments, the bypass portion  825  may form a proximal extension of the cutting needle  810 . 
     In some embodiments, the bypass portion  825  is substantially similar to the bypass portion  425  described above in relation to  FIGS. 4 and 5 , except for the differences described herein. The inner diameter may vary between the distal portion  824 , the bypass portion  825 , and the proximal portion  826  as described in relation to the handpiece  400 . In other embodiments, an inner diameter D7 of the bypass portion  825  may be substantially the same as an inner diameter D6 of the distal portion  824  and/or an inner diameter D8 of the proximal portion  826 . For example, in the pictured embodiment in  FIG. 8 , the inner diameter D7 of the bypass portion  825  is larger than the inner diameter D6 of the distal portion  824 , but is substantially the same as the inner diameter D8 of the proximal portion  826 . 
     As shown in  FIG. 8 , the bypass portion  825  comprises a housing  827  having an inner surface  828  and an outer surface  829 . The inner surface  828  is in contact with the aspirated fluid and tissue material within the aspiration lumen  821  of the aspiration channel  820 . The outer surface  829  is in contact with the irrigation passageway  817 . 
       FIG. 9  illustrates a cross-sectional view of the bypass portion  825  along the line 9-9 according to one embodiment consistent with the principles of the present disclosure. The bypass portion  825  is substantially similar to the bypass portion  625  described above with relation to  FIGS. 6 and 7  except for any differences described herein. As shown in  FIGS. 8 and 9 , the bypass portion  825  includes two bypass ports,  830   a  and  830   b , which are disposed opposite each other at a substantially identical longitudinal distance along the aspiration channel  820  from the distal tip  819 . The bypass ports  830   a ,  830   b  fluidically connect the aspiration lumen  821  with the irrigation passageway  817 . It should be understood that a varying number of bypass ports  830  can be used and that the bypass ports  830  may be arranged on the bypass portion  825  in any of a variety of patterns. 
     As mentioned above, the irrigation sleeve  815  includes the chamber  880 , which comprises an annular space disposed entirely within the irrigation sleeve  815 . The irrigation sleeve  815  also includes the sealing element  850 , which is disposed on the irrigation sleeve  815  between the chamber  880  and the irrigation passageway  817 . As shown in  FIG. 7 , the sealing element  850  is disposed on the irrigation sleeve  815  such that the chamber  880 , the sealing element  850 , and the bypass port  830   a  are coaxially aligned about a central axis CA extending through the bypass port  830   a . The chamber  880  may contain a predetermined volume of fluid, such a gas or a liquid. The chamber  880  is fluid-tight, so compression of the chamber  880  results in deformation of the chamber  880  and movement of the sealing element  850 . 
     The sealing element  850  comprises a flexible, displaceable portion of the irrigation sleeve  815  that may shift onto the bypass port  830   a  to reduce or eliminate flow through the bypass port  830   a . In the pictured embodiment in  FIGS. 8 and 9 , the sealing element  850  comprises an “M”-shaped, button-like structure. The sealing element  850  includes a first side  855  and an opposing second side  860 . The first side  855  faces the chamber  880  and is substantially continuous with a chamber surface  865  of the irrigation sleeve  815 . The second side  860  is substantially continuous with an interior surface  870  of the irrigation sleeve  815 . The second side  860  is shaped and configured to block flow through the bypass port  830   a  when the sealing element  850  contacts the bypass port  830   a . In particular, the second side  860  is shaped and configured to block flow through the bypass port  830   a  when the sealing element  850  is depressed inward to contact the outer surface  829  of the housing  827  of the bypass potion  825 . In some embodiments, the second side  860  may deform under pressure to seat at least partially within the bypass port  830   a.    
     As illustrated in  FIGS. 8-11 , the sealing element  850  includes a central section  875  and a peripheral section  885 , which circumferentially surrounds the central section  875 . As shown in detail in  FIG. 10 , the sealing element  850  contacts the irrigation sleeve  815  at the peripheral section  885 . In the pictured embodiment, the central section  875  is substantially thicker than the peripheral section  885 . The peripheral section  885  is curved to facilitate the inward and outward movement of the sealing element  850 . In other embodiments, the peripheral section  885  is substantially flat. The sealing element  850  is shaped and configured to offer the area within the chamber  880  of least resistance to deformation. 
     Thus, as shown in  FIG. 11 , when the chamber  880  is compressed or force is applied to the irrigation sleeve  815  (e.g., by a user physically compressing the irrigation sleeve  815 ) and pressure increases within the chamber  880 , the peripheral section  885  deforms and the central section  875  of the sealing element  850  moves toward the housing  827  of the bypass portion  825 . It is important to note that the user may apply force on any portion of the irrigation sleeve  815  surrounding the annular chamber  880  in order to increase pressure within the chamber  880  and shift the sealing element  850  toward the bypass port  830   a . Thus, in order to increase the aspiration vacuum within the aspiration lumen  821 , the user need not position or reposition his or her hand to compress the area of the irrigation sleeve  815  overlying or adjacent to the sealing element  850 . Instead, the user can simply apply pressure to the irrigation sleeve  815  anywhere surrounding the chamber  880 . When the second side  860  of the sealing element  850  contacts the outer surface  829  of the housing  827 , the sealing element  850  blocks the ingress and/or egress of fluid and tissue through the bypass port  830   a . When the sealing element  850  blocks the bypass port  830   a , the vacuum pressure within the aspiration lumen  821  rapidly increases. 
     In some embodiments, the sealing element  850  may be formed as an integral part of the irrigation sleeve  815 . In other embodiments, the sealing element  850  may be formed as a separate component of the handpiece  800  that is fixedly attached to the irrigation sleeve  815  by the peripheral section  885  by welding, overmolding, adhesive, or any other suitable means for fixedly attaching the sealing element  850  to the irrigation sleeve  815  in a fluid-tight fashion. The irrigation sleeve  815  and/or the sealing element  850  may be formed of any of a variety of suitable flexible materials, including, by way of non-limiting example, silicon, nitrile rubber, and polyisoprene. 
     While using handpieces capable of producing a rapid increase in aspiration vacuum to 700 mmHg or more within a short time (e.g., 20 to 30 milliseconds), the user may control the vacuum pressure by utilizing the bypass ports (e.g., bypass ports  830   a ,  830   b ) and varying the overall aspiration flow rate. In general, the resulting tip vacuum pressure produced at a specific aspiration flow rate is highly repeatable and predictable. In some applications, however, very high vacuum pressures may be desirable for very brief periods of time, including, by way of non-limiting example, during an occlusion of the distal tip  819  of the aspiration channel  820  to clear the occlusion. In some applications, rapid increases in vacuum pressure may improve the purchase of lens material when the distal tip  819  contacts the lens material. 
     A user employing the handpiece  800  may rapidly increase the tip vacuum pressure within the aspiration lumen  820  without necessarily changing the aspiration flow rate. Because the chamber  880  is fluid-tight and extends circumferentially around the aspiration lumen  820 , and because the sealing element  850  is the area of least resistance within the chamber  880 , a user may compress any portion of the chamber  880  to increase the pressure within the chamber  880  and cause the sealing element  850  to shift and block the bypass port  830   a . In particular, the user may compress the irrigation sleeve  815  anywhere around the circumference of the sleeve  815  in the area of the chamber  880  to increase pressure within the chamber  880  until the sealing element  850  contacts the bypass port  830   a . This enables the user to block the bypass port  830   a  without necessarily reorienting the handpiece  800  or repositioning his grip of the handpiece  800 . When the sealing element  850  contacts the bypass port  830   a , the vacuum pressure within the aspiration lumen  821  rapidly increases. The handpiece  800  allows the user more real-time control over aspiration vacuum pressures during ophthalmic surgeries, for example in response to occlusions within the aspiration lumen  821 . 
     By using the embodiments disclosed herein to control the bypass volume and flow rate, the vacuum at the tip can be actively controlled to achieve the very low tip vacuum levels required for certain ophthalmic applications (e.g., without limitation, capsule polishing), while also allowing the user to selectively increase the tip vacuum for tissue aspiration by depressing the sealing element  650 ,  850  (e.g., either directly as in handpiece  600  or by applying force to the silicone sleeve  815  in the handpiece  800 ). Depressing the sealing element  650 ,  850  onto the bypass port  630   a ,  830   a , respectively, reduces the bypass volume at a specific flow rate and almost immediately increases the tip vacuum level. Releasing force on the sealing element  650 ,  850  allows flow to resume through the bypass port  630   a ,  830   a  and almost immediately decreases the tip vacuum level or restores the original tip vacuum level (e.g., as dictated by the control console  120 ). 
     Embodiments in accordance with the present disclosure provide users with an instrument having at least one bypass port in area of increased internal diameter within the aspiration channel, thereby reducing the risk of inadvertent increases in aspiration vacuum pressures secondary to blockage of the bypass port. Some embodiments provide users with an instrument that enables the user to selectively increase the vacuum within the aspiration tip/lumen (e.g., in order to capture and aspirate unwanted tissue) by depressing a button or sealing element to block at least one bypass port without adjusting the preset aspiration flow rate. Releasing the force applied to the button allows flow to resume through the bypass port(s), thus reducing the vacuum pressures within the aspiration lumen/tip. Some embodiments provide users with an instrument that enables the user to selectively increase the vacuum within the aspiration tip/lumen by compressing the irrigation sleeve to block at least one bypass port without adjusting the preset aspiration flow rate, reorienting the instrument, or reorienting the user&#39;s grip on the instrument. Releasing the force applied to the irrigation sleeve allows flow to resume through the bypass port(s), thus reducing the vacuum pressures within the aspiration lumen/tip. 
     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