Patent Publication Number: US-2010130944-A1

Title: Flow control devices for ophthalmic surgery

Description:
BACKGROUND 
     1. Field 
     The present disclosure directed to flow control devices for controlling fluid flow during ophthalmic surgeries. 
     2. Description of the Related Art 
     The statements in this section merely provide background information related to the present disclosure and may not constitute prior art. 
     In surgery, particularly eye surgery, surgery systems are commonly used to generate fluid flow to and from a surgical site. Irrigation provides fluid to the surgical site, while aspiration removes fluid and debris from the surgical site. In ophthalmic surgery, balancing the irrigation and aspiration is necessary for several reasons, including keeping the eye inflated and preventing collapse of the eye, which may cause serious damage. 
     During ophthalmic surgery, aspiration is used by a surgeon to evacuate debris from the surgical site. In phacoemulsification, for example, a surgical handpiece fitted with an ophthalmic needle is used to break apart a cataract and provide an aspiration path for evacuating cataract debris from the eye. The surgeon may employ aspiration to hold the cataract prior to applying ultrasonic energy to the cataract with the ophthalmic needle coupled to one end of the surgical handpiece. By holding the cataract, the ophthalmic needle may be partially or wholly occluded, often resulting in pressure building through a fluid path from the surgery site to the surgery system housing an aspiration pump and collection reservoir. Debris from the cataract may also partially or wholly occlude the ophthalmic needle. As pressure in the infusion fluid path increases during occlusion, fluid behind the occlusion is aspirated creating an ever increasing vacuum level. When the occlusion is removed, an inrush of fluid from the eye may cause an imbalance in irrigation/aspiration sufficient to cause damage to the eye. In order to prevent or at least minimize the chances of the damage resulting from occlusion, it is desirable to control fluid aspiration flow by increasing flow resistance to aspiration between the surgical handpiece and the surgery system. Increasing flow resistance also generally permits a higher level of vacuum to be maintained that, in turn, provides for a greater level of purchase or followability of the cataract to the needle, which is desirable to the surgeon. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The drawings described herein are for illustration purposes only and are not intended to limit the scope of the present disclosure in any way. 
         FIG. 1  is a perspective view of a flow control device according to the present disclosure; 
         FIG. 2  is an elevation view of the a flow control device of  FIG. 1 ; 
         FIG. 3  is a cross-sectional view of the flow control device of  FIG. 2  along line  3 - 3 ; 
         FIG. 4  is an elevation view of the a flow control device of  FIG. 1  along line  4 - 4 ; 
         FIG. 5  is a perspective view of a surgical handpiece assembly including a flow control device according to the present disclosure; and 
         FIG. 6  is a cut-away perspective new of another flow control device according to the present disclosure. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     The following description is merely exemplary in nature and is not intended to limit the present disclosure, application, or uses. 
     According to one embodiment of the present disclosure, a flow control device  10  is illustrated in  FIG. 1 . The flow control device  10  includes a chamber  12  having two sides  14  in parallel separated by a height, an inlet port  16  extending tangentially from the chamber in parallel with the two sides, and an outlet port  18  extending from the center of the chamber perpendicular to the two sides. In use, the inlet port  16  couples to a surgical handpiece, and the outlet port  18  couples aspiration tubing for transporting fluid between the surgical handpiece and a collection reservoir in an ophthalmic surgery system. The flow control device  10  helps maintain intraocular pressure in an eye by controlling aspiration fluid flow from the eye by increasing aspiration fluid flow resistance. 
     The inlet port  16  defines an opening, and the outlet port  18  defines an opening. The cross-section area of the opening of the outlet port  18  is preferably at least equal to the cross-sectional area of the opening of the inlet port  16 . In this manner, any debris entering the flow control device  10  via the inlet port  16  is able to exit the flow control device  10  through the outlet port  18  such that a potential for clogging fluid flow through the flow control device  10  is eliminated. It should be appreciated that a cross-sectional area of an opening of an inlet port or an outlet port may also be selected to provide a particular flow rate through a flow control device. 
       FIG. 2  shows an elevation view of the flow control device  10 , which defines a generally circular cross-section in parallel with sides  14 . It should be appreciated that other cross-sectional shapes may be employed to affect flow resistance through flow control devices according to other embodiments of the present disclosure. For example, a chamber of a flow control device may define an ovular, a rectangular, or a triangular cross-section. 
     The flow control device  10  is formed from any medical grade material including metal or plastics. A different type of material may be included in a different flow control device for various reasons, such as cost, flexibility, manufacturability, suitability for use in medical procedures, etc. 
       FIG. 3  shows a cross-section view of the flow control device  10  through line  3 - 3  in  FIG. 2 . As shown, the outlet port  18  extends from the center of the generally circular cross-section of the chamber  12 . It should be appreciated that in other embodiments, an outlet port may offset from the center of the cross-section of the chamber.  FIG. 3  further illustrates that the chamber  12  is hollow. By being hollow, flow resistance through the flow control device  10  is generally defined by the shape and dimensions of the chamber  12 , as well as relative locations of the inlet port  16  and the outlet port  18 . In other embodiments, it should be appreciated that a divider, a partition or another impingement to fluid flow may be included in a flow control device to increase or decrease flow resistance through the flow control device. 
     The generally circular cross-section includes a radius  20  denoted in  FIG. 3 . The radius  20  may be selected in combination with a height  22  of the chamber  12 , referred to above. For example, a radius of a chamber having a generally circular cross-sectional may be at least two times a height of the chamber in at least one embodiment. It is desirable that the radius  20  be greater than the height  22  thereby providing a ratio of the radius to the height greater than 1. Generally, for a flow control device, according to the present disclosure, as the ratio increases, flow resistance between an inlet port and an outlet port also increases. 
     Flow resistance is generally dependent on the particular dimensions of the flow control device  10 . Specifically, the ratio of the radius  20  to the height  22 . For example, the radius  20  may be about 15 mm and the height about 1.5 mm. Therefore the ratio of the radius  20  to the height  22  is 10:1. The greater the ratio, the higher the flow resistance at any given flow rate. The higher the flow rate, the greater the resistance. With these two relationships, it is possible to select both absolute sizes and the ratio to achieve the desired resistance curve in relation to flow. It is believed that the physics creating resistance is primarily the conservation of angular momentum causing the flow to rotate ever faster as the fluid moves toward the center exit port. This spin produces shear forces between advacent fluid segment as well as flow resistance with the chamber walls. The inlet port and outlet port sizes are suitable to couple to known aspiration ports of the surgical handpieces. The height  22  can be considerably smaller than the inlet port if a clear path about the circumference of the device is at least the size of the inlet port. See discussion of  FIG. 6  below. This allows particles to revolve in the fluid but not get lodged in the space created by the parallel walls separated by the device height  22 . It should be appreciated that one or move of the dimensions may be increased or decreased for different flow resistances, other types of surgical handpieces and/or aspiration tubing, or other reasons related to performance, use or aesthetics. 
       FIG. 4  shows an elevation view of the flow control device  10  taken along line  4 - 4 . As illustrated, the diameter of the inlet port  16  is substantially equal to the height  22  of the flow control device  10 . In some embodiments, it is desirable that a height of a chamber be at least substantially equal to an aspiration port of a handpiece or aspiration tubing coupled to an inlet port of the flow control device. Accordingly, it should be understood that different size and shapes of inlet ports and chamber may be employed in a flow control device depending on a particular handpiece or aspiration tubing of an implementation. 
       FIG. 5  shows a surgical handpiece assembly  24 . The surgical handpiece assembly  24  includes aspiration tubing  26  for coupling to a surgery system (not shown) and a surgical handpiece  28  having an ophthalmic needle  30  and an aspiration port  32 . The surgical handpiece  28 , in combination with the aspiration tubing  26  and the surgery system (not shown), is configured to transport aspiration fluid exiting the aspiration port  32  and debris from a surgical site during a phacoemulsification surgery procedure. 
     The surgical handpiece assembly  24  also includes the flow control device  34 . The flow control device  34  includes a chamber  36 , an inlet port  38 , and an outlet port  40 . The outlet port  40  is connected to the aspiration tubing, and the inlet port  38  is coupled to the aspiration port  32  of the surgical handpiece  28 . The flow control device  34  is preferably coupled between to the surgical handpiece  28  aspiration port  32  and aspiration tubing  26 . In other embodiments, a flow control device may be coupled at a different point along a fluid path between a surgical handpiece and a surgery system. Accordingly, a flow control device may be connected directly to an aspiration port of a surgical handpiece or via a length of aspiration tubing. 
     The inlet port  38  includes an opening with a cross-sectional area, and the aspiration port  32  of the surgical handpiece  28  also includes an opening with a cross-sectional area. It is preferable for the cross-sectional area of the opening of the inlet port  38  to be greater than the cross-sectional area of the opening of the aspiration port  32 , such that inlet port is configured to matingly connect to aspiration port  32 . In this manner, any debris transported through the aspiration port  32  likely flows through the inlet port  38  without clogging and thereby interrupting fluid flow through the flow control device  32 . The outlet port  40  also includes an opening with a cross-sectional area. Similarly, it is preferable for the cross-sectional area of the opening of the outlet port  40  be at least equal to the cross-sectional area of the opening of the inlet port  38 . 
       FIG. 6  shows a cut-away perspective view of another flow control device  42 . Device  42  functions and is constructed similarly to device  10  described above. The difference between device  10  and device  42  is central indented portion  44  opposite outlet  46 . Central portion  44  in the chamber side opposite outlet port  46  and the chamber side with the outlet port  46  define a central height  48  that is much smaller than the height  50  separating the two chamber sides. Having central height  48  be much smaller than height  50 , allows device  42  to achieve dimension ratios of radius to height (as discussed above) that would be difficult to achieve with device  10 . This is because without the overall height  48 , the radius of device  10  would be required to be so large as to be impractical to use in surgery. Placing portion  44  centrally relative to outlet  46  allows aspirated particles to flow about the periphery having height  50  without clogging the space defined by height  48  and without requiring a filter before fluid enters device  42 . 
     Certain terminology is used herein for purposes of reference only, and thus is not intended to be limiting. For example, terms such as “upper,” “lower,” “above,” “below,” “top,” “upward,” and “downward” refer to directions in the drawings to which reference is made. Terms such as “front,” “back,” “rear,” and “side,” describe the orientation of portions of the component within a consistent but arbitrary frame of reference which is made clear by reference to the text and the associated drawings describing the component under discussion. Such terminology may include the words specifically mentioned above, derivatives thereof, and words of similar import. 
     Although several aspects of the present disclosure have been described above with reference to aspiration during ophthalmic surgeries, it should be understood that various aspects of the present disclosure are not limited to aspiration during ophthalmic surgeries, and can be applied to a variety of other ophthalmic surgical procedures and methods. 
     By implementing any or all of the teachings described above, a number of benefits and advantages can be attained including improved reliability, reduced down time, elimination or reduction of redundant components or systems, avoiding unnecessary or premature replacement of components or systems, and a reduction in overall system and operating costs.