Patent Publication Number: US-2011071454-A1

Title: Power Generator For Glaucoma Drainage Device

Description:
This application is a continuation-in-part of U.S. application Ser. No. 12/609,043 filed Oct. 30, 2009, which is a continuation-in-part of U.S. application Ser. No. 12/563,244 filed Sep. 21, 2009. 
    
    
     BACKGROUND OF THE INVENTION 
     The present invention relates to a glaucoma drainage device with an active, reciprocating member that acts to clear the lumen, prevent fibrosis, and/or properly disperse aqueous. 
     Glaucoma, a group of eye diseases affecting the retina and optic nerve, is one of the leading causes of blindness worldwide. Glaucoma results when the intraocular pressure (IOP) increases to pressures above normal for prolonged periods of time. IOP can increase due to an imbalance of the production of aqueous humor and the drainage of the aqueous humor. Left untreated, an elevated IOP causes irreversible damage the optic nerve and retinal fibers resulting in a progressive, permanent loss of vision. 
     The eye&#39;s ciliary body epithelium constantly produces aqueous humor, the clear fluid that fills the anterior chamber of the eye (the space between the cornea and iris). The aqueous humor flows out of the anterior chamber through the uveoscleral pathways, a complex drainage system. The delicate balance between the production and drainage of aqueous humor determines the eye&#39;s IOP. 
     Open angle (also called chronic open angle or primary open angle) is the most common type of glaucoma. With this type, even though the anterior structures of the eye appear normal, aqueous fluid builds within the anterior chamber, causing the IOP to become elevated. Left untreated, this may result in permanent damage of the optic nerve and retina. Eye drops are generally prescribed to lower the eye pressure. In some cases, surgery is performed if the IOP cannot be adequately controlled with medical therapy. 
     Only about 10% of the population suffers from acute angle closure glaucoma. Acute angle closure occurs because of an abnormality of the structures in the front of the eye. In most of these cases, the space between the iris and cornea is more narrow than normal, leaving a smaller channel for the aqueous to pass through. If the flow of aqueous becomes completely blocked, the IOP rises sharply, causing a sudden angle closure attack. 
     Secondary glaucoma occurs as a result of another disease or problem within the eye such as: inflammation, trauma, previous surgery, diabetes, tumor, and certain medications. For this type, both the glaucoma and the underlying problem must be treated. 
       FIG. 1  is a diagram of the front portion of an eye that helps to explain the processes of glaucoma. In  FIG. 1 , representations of the lens  110 , cornea  120 , iris  130 , ciliary bodies  140 , trabecular meshwork  150 , and Schlemm&#39;s canal  160  are pictured. Anatomically, the anterior chamber of the eye includes the structures that cause glaucoma. Aqueous fluid is produced by the ciliary bodies  140  that lie beneath the iris  130  and adjacent to the lens  110  in the anterior chamber. This aqueous humor washes over the lens  110  and iris  130  and flows to the drainage system located in the angle of the anterior chamber. The angle of the anterior chamber, which extends circumferentially around the eye, contains structures that allow the aqueous humor to drain. The first structure, and the one most commonly implicated in glaucoma, is the trabecular meshwork  150 . The trabecular meshwork  150  extends circumferentially around the anterior chamber in the angle. The trabecular meshwork  150  seems to act as a filter, limiting the outflow of aqueous humor and providing a back pressure producing the IOP. Schlemm&#39;s canal  160  is located beyond the trabecular meshwork  150 . Schlemm&#39;s canal  160  has collector channels that allow aqueous humor to flow out of the anterior chamber. The two arrows in the anterior chamber of  FIG. 1  show the flow of aqueous humor from the ciliary bodies  140 , over the lens  110 , over the iris  130 , through the trabecular meshwork  150 , and into Schlemm&#39;s canal  160  and its collector channels. 
     In glaucoma patients, IOP can vary widely during a 24 hour period. Generally, IOP is highest in the early morning hours before medication is administered upon waking. Higher pressures damage the optic nerve and can lead to blindness. Accordingly, it would be desirable to have an active glaucoma drainage device that controls IOP. In order to power such a device, it would desirable to have a power source that harnesses the pressure differential between the anterior chamber and a drainage location. 
     SUMMARY OF THE INVENTION 
     In one embodiment consistent with the principles of the present invention, the present invention is a glaucoma drainage device that has a tube shunting the anterior chamber to a drainage location. A power generator has a rotor coupled to a micro-generator. The power generator is configured to generate energy from aqueous flowing through the tube. The force required to drive the rotor can be controlled to control the flow of aqueous through the tube. 
     It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are intended to provide further explanation of the invention as claimed. The following description, as well as the practice of the invention, set forth and suggest additional advantages and purposes of the invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate several embodiments of the invention and together with the description, serve to explain the principles of the invention. 
         FIG. 1  is a diagram of the front portion of an eye. 
         FIG. 2  is a block diagram of an IOP measuring system according to the principles of the present invention. 
         FIG. 3  is a diagram of an IOP sensor according to the principles of the present invention. 
         FIG. 4  is a diagram of one possible application of the IOP sensor of the present invention. 
         FIG. 5  is an end cap implementation of an IOP sensor consistent with the principles of the present invention. 
         FIGS. 6A and 6B  are perspective views of an end cap implementation of an TOP sensor consistent with the principles of the present invention. 
         FIGS. 7A and 7B  are perspective views of a lumen clearing valve according to the principles of the present invention. 
         FIG. 8  is a perspective view of a lumen clearing valve with a fiber clearing member according to the principles of the present invention. 
         FIG. 9  is a perspective view of a lumen clearing valve with an aqueous dispersion member to clear fibrosis according to the principles of the present invention. 
         FIG. 10  is a perspective view of a lumen clearing valve with hybrid external member according to the principles of the present invention. 
         FIGS. 11A and 11B  depict an end cap implementation of the valve and pressure sensor system according to the principles of the present invention that includes both single and dual lumen versions. 
         FIGS. 12A and 12B  are cross section views of dual tubing that can be used with the system of the present invention. 
         FIG. 13  is a perspective view of a two lumen valve and pressure sensor system according to the principles of the present invention. 
         FIG. 14  is a perspective view of power generator according to the principles of the present invention. 
         FIG. 15  is an end view of a rotor located in a tube according to the principles of the present invention. 
         FIG. 16  is a diagram of one possible location of a power generator in a glaucoma drainage system according to the principles of the present invention. 
         FIG. 17  is a diagram of another possible location of a power generator in a glaucoma drainage system according to the principles of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Reference is now made in detail to the exemplary embodiments of the invention, examples of which are illustrated in the accompanying drawings. Wherever possible, the same reference numbers are used throughout the drawings to refer to the same or like parts. 
       FIG. 2  is a block diagram of an IOP measuring system  200  according to the principles of the present invention. In  FIG. 2 , the IOP measuring system includes power source  205 , IOP sensor  210  (which can include P 1 , P 2 , and/or P 3 ), processor  215 , memory  220 , data transmission module  225 , and optional speaker  230 . 
     Power source  205  is typically a rechargeable battery, such as a lithium ion or lithium polymer battery, although other types of batteries may be employed. In addition, any other type of power cell is appropriate for power source  205 . Power source  205  provides power to the system  200 , and more particularly to processor  215 . Power source can be recharged via an RFID link or other type of magnetic coupling. 
     In another embodiment of the present invention, power source  205  is a capacitor that stores charge generated by generator  1410  as explained below. Other types of charge storing or energy storing devices may also be employed to implement power source  205 . As more fully explained below, generator  1410  is coupled to power source  205 . 
     Processor  215  is typically an integrated circuit with power, input, and output pins capable of performing logic functions. In various embodiments, processor  215  is a targeted device controller. In such a case, processor  215  performs specific control functions targeted to a specific device or component, such as a data transmission module  225 , speaker  230 , power source  205 , or memory  220 . In other embodiments, processor  215  is a microprocessor. In such a case, processor  215  is programmable so that it can function to control more than one component of the device. In other cases, processor  215  is not a programmable microprocessor, but instead is a special purpose controller configured to control different components that perform different functions. 
     Memory  220  is typically a semiconductor memory such as NAND flash memory. As the size of semiconductor memory is very small, and the memory needs of the system  200  are small, memory  220  occupies a very small footprint of system  200 . Memory  220  interfaces with processor  215 . As such, processor  215  can write to and read from memory  220 . For example, processor  215  can be configured to read data from the IOP sensor  210  and write that data to memory  220 . In this manner, a series of IOP readings can be stored in memory  220 . Processor  215  is also capable of performing other basic memory functions, such as erasing or overwriting memory  220 , detecting when memory  220  is full, and other common functions associated with managing semiconductor memory. 
     Data transmission module  225  may employ any of a number of different types of data transmission. For example, data transmission module  225  may be active device such as a radio. Data transmission module  225  may also be a passive device such as the antenna on an RFID tag. In this case, an RFID tag includes memory  220  and data transmission module  225  in the form of an antenna. An RFID reader can then be placed near the system  200  to write data to or read data from memory  220 . Since the amount of data typically stored in memory  220  is likely to be small (consisting of IOP readings over a period of time), the speed with which data is transferred is not crucial. Other types of data that can be stored in memory  220  and transmitted by data transmission module  225  include, but are not limited to, power source data (e.g. low battery, battery defect), speaker data (warning tones, voices), IOP sensor data (IOP readings, problem conditions), and the like. 
     Optional speaker  230  provides a warning tone or voice to the patient when a dangerous condition exists. For example, if IOP is at a level that is likely to lead to damage or presents a risk to the patient, speaker  230  may sound a warning tone to alert the patient to seek medical attention or to administer eye drops. Processor  215  reads IOP measurements from IOP sensor  210 . If processor  215  reads one or a series of IOP measurements that are above a threshold, then processor  215  can operate speaker  230  to sound a warning. The threshold can be set and stored in memory  220 . In this manner, an IOP threshold can be set by a doctor, and when exceeded, a warning can be sounded. 
     Alternatively, data transmission module may be activated to communicate an elevated IOP condition to a secondary device such as a PDA, cell phone, computer, wrist watch, custom device exclusively for this purpose, remote accessible data storage site (e.g. an internet server, email server, text message server), or other electronic device. In one embodiment, a personal electronic device uploads the data to the remote accessible data storage site (e.g. an internet server, email server, text message server). Information may be uploaded to a remote accessible data storage site so that it can be viewed in real time, for example, by medical personnel. In this case, the secondary device may contain the speaker  230 . For example, in a hospital setting, after a patient has undergone glaucoma surgery and had system  200  implanted, a secondary device may be located next to the patient&#39;s hospital bed. Since IOP fluctuations are common after glaucoma surgery (both on the high side and on the low side which is also a dangerous condition), processor  215  can read IOP measurements made by an implanted IOP sensor  210 . If processor  215  reads an unsafe IOP condition, data transmission module  225  can alert the patient and medical staff via speaker  230  or by transmitting the unsafe readings to a secondary device. 
     Such a system is also suitable for use outside a hospital setting. For example, if an unsafe IOP condition exists, processor  215  can operate speaker  230  to sound an audible warning. The patient is then alerted and can seek medical attention. The warning can be turned off by a medical professional in a number of ways. For example, when data transmission module  225  is an RFID tag, an RFID link can be established between an external device and system  200 . This external device can communicate with system  200  to turn off the speaker  230 . Alternatively, an optical signal may be read by system  200 . In this case, data transmission module  225  has an optical receptor that can receive a series of light pulses that represent a command—such as a command to turn off speaker  230 . 
       FIG. 3  is a diagram of an IOP sensor according to the principles of the present invention. In  FIG. 3 , the IOP sensor consists of three pressure sensors, P 1 , P 2 , and P 3 , a drainage tube  430 , valve  420 , and divider  350 . Pressure sensor P 1  is located in or is in fluidic communication with the anterior chamber  340 , pressure sensor P 2  is located at a drainage site in the subconjunctival space, and pressure sensor P 3  is located remotely from P 1  and P 2 . Pressure sensor P 1  can also be located in a lumen or tube that is in fluid communication with the anterior chamber. As such, pressure sensor P 1  measures a pressure in the anterior chamber, pressure sensor P 2  measures a pressure at a drainage site, and pressure sensor P 3  generally measures or corresponds to atmospheric pressure. 
     In  FIG. 3 , tube  430  drains aqueous from the anterior chamber  340  of the eye. A valve  420  controls the flow of aqueous through the tube  430 . Pressure sensor P 1  measures the pressure in the tube  430  upstream from the valve  420  and downstream from the anterior chamber  340 . In this manner, pressure sensor P 1  measures the pressure in the anterior chamber  340 . The expected measurement discrepancy between the true anterior chamber pressure and that measured by P 1  when located in a tube downstream of the anterior chamber (even when located between the sclera and the conjunctiva) is very minimal. For example, Poiseuille&#39;s law for pipe flow predicts a pressure drop of 0.01 mmHg across a 5-millimeter long tube with a 0.300 millimeter inner diameter for a flow rate of 3 microliters per minute of water. 
     A divider  350  separates pressure sensor P 2  from pressure sensor P 3 . Pressure sensor P 2  is located at a drainage site (e.g.  410  in  FIG. 4 ). As such, pressure sensor P 2  is located in a pocket that generally contains aqueous—it is in a wet location  410 . Pressure sensor P 3  is physically separated from pressure sensor P 2  by divider  350 . Divider  350  is a physical structure that separates the wet location  410  of P 2  from the dry location  360  of P 3 . Divider  350  is included when the system of the present invention is located on a single substrate. In this configuration, all three pressure sensors (P 1 , P 2 , and P 3 ) are located on a substrate that includes tube  430 , valve  420 , divider  350 , and the other components of the system. 
     In one embodiment of the present invention, pressure sensor P 3  is located in close proximity to the eye. Pressure sensor P 3  may be implanted in the eye under the conjunctiva. In such a case, pressure sensor P 3  measures a pressure that can be correlated with atmospheric pressure. For example, true atmospheric pressure can be a function of the pressure reading of pressure sensor P 3 . P 3  may also be located in a dry portion  360  of the subconjunctival space, separate from the drainage location. Regardless of location, pressure sensor P 3  is intended to measure atmospheric pressure in the vicinity of the eye or at the eye&#39;s surface. 
     Generally, IOP is a gauge pressure reading—the difference between the absolute pressure in the eye (as measured by P 1 ) and atmospheric pressure (as measured by P 3 ). Atmospheric pressure, typically about 760 mm Hg, often varies in magnitude by 10 mmHg or more. In addition, the effective atmospheric pressure can vary significantly—in excess of 100 mmHg—if a patient goes swimming, hiking, riding in airplane, etc. Such a variation in atmospheric pressure is significant since IOP is typically in the range of about 15 mm Hg. Thus, for 24 hour monitoring of IOP, it is desirable to have pressure readings for the anterior chamber (as measured by P 1 ) and atmospheric pressure in the vicinity of the eye (as measured by P 3 ). 
     Therefore, in one embodiment of the present invention, pressure readings are taken by P 1  and P 3  simultaneously or nearly simultaneously over time so that the actual IOP can be calculated (as P 1 -P 3  or P 1 - f (P 3 )). The pressure readings of P 1  and P 3  can be stored in memory  220  by processor  215 . They can later be read from memory so that actual IOP over time can be interpreted by a physician. 
     Pressure sensors P 1 , P 2 , and P 3  can be any type of pressure sensor suitable for implantation in the eye. They each may be the same type of pressure sensor, or they may be different types of pressure sensors. For example, pressure sensors P 1  and P 2  may be the same type of pressure sensor (implanted in the eye), and pressure sensor P 3  may be a different type of pressure sensor (in the vicinity of the eye). 
     In another embodiment of the present invention, pressure readings taken by pressure sensors P 1  and P 2  can be used to control a device that drains aqueous from the anterior chamber  340 .  FIG. 4  is a diagram of one possible application of the IOP sensor of the present invention that utilizes the readings of pressures sensors P 1  and P 2 . In  FIG. 4 , pressure sensor P 1  measures the pressure in the anterior chamber  340  of the eye. Pressure sensor P 2  measures the pressure at a drainage site  410 . 
     Numerous devices have been developed to drain aqueous from the anterior chamber  340  to control glaucoma. Most of these devices are variations of a tube that shunts aqueous from the anterior chamber  340  to a drainage location  410 . For example, tubes have been developed that shunt aqueous from the anterior chamber  340  to the subconjunctival space thus forming a bleb under the conjunctiva or to the subscleral space thus forming a bleb under the sclera. (Note that a bleb is a pocket of fluid that forms under the conjunctiva or sclera). Other tube designs shunt aqueous from the anterior chamber to the suprachoroidal space, the supraciliary space, the juxta-uveal space, or to the choroid. In other applications, tubes shunt aqueous from the anterior chamber to Schlemm&#39;s canal, a collector channel in Schlemm&#39;s canal, or any of a number of different blood vessels like an episcleral vein. Some tubes even shunt aqueous from the anterior chamber to outside the conjunctiva. Finally, in some applications, no tube is used at all. For example, in a trabeculectomy (or other type of filtering procedure), a small hole is made from the subconjunctival or subscleral space to the anterior chamber. In this manner, aqueous drains from the anterior chamber, through the hole, and to a bleb under the conjunctiva or sclera. Each of these different anatomical locations to which aqueous is shunted is an example of a drainage location  410 . 
     In  FIG. 4 , a tube  430  with a valve  420  on one end is located with one end in the anterior chamber  340  and the other end in a drainage location  410 . In this manner, the tube  430  drains aqueous from the anterior chamber  340  to the drainage location  410 . Valve  420  controls the flow of aqueous from anterior chamber  340  to drainage location  410 . Pressure sensor P 1  is located in the anterior chamber or in fluid communication with the anterior chamber  340 . As shown in the embodiment of  FIG. 3 , pressure sensor P 1  is located upstream from valve  420 . In this manner, pressure sensor P 1  is located in the subconjunctival space but is in fluid communication with the anterior chamber  340 . 
     Since pressure sensor P 1  measures the pressure in the anterior chamber  340  and pressure sensor P 2  measures pressure at the drainage location  410 , the difference between the readings taken by these two pressure sensors (P 1 -P 2 ) provides an indication of the pressure differential between the anterior chamber  340  and the drainage location  410 . In one embodiment, this pressure differential dictates the rate of aqueous flow from the anterior chamber  340  to the drainage location  410 . 
     One complication involved with filtering surgery that shunts the anterior chamber  340  to a drainage location  410  is hypotony—a dangerous drop in IOP that can result in severe consequences. It is desirable to control the rate of aqueous outflow from the anterior chamber  340  to the drainage location  410  so as to prevent hypotony. Readings from pressure sensor P 1  and pressure sensor P 2  can be used to control the flow rate through tube  430  by controlling valve  420 . For example, valve  420  can be controlled based on the pressure readings from pressure sensor P 1  and pressure sensor P 2 . 
     In another embodiment of the present invention, IOP (based on readings from pressure sensor P 1  and pressure sensor P 3 ) can be controlled by controlling valve  420 . In this manner, IOP is the control parameter. Valve  420  can be adjusted to maintain a particular IOP (like an IOP of 15 mm Hg). Valve  420  may be opened more at night than during the day to maintain a particular IOP. In other embodiments, an IOP drop can be controlled. Immediately after filtering surgery, IOP can drop precipitously. Valve  420  can be adjusted to permit a gradual drop in IOP based on readings from pressure sensors P 1  and P 3 . 
     In another embodiment of the present invention, readings from pressure sensor P 2  (or from the difference between pressure sensor P 2  and atmospheric pressure as measured by P 3 ) can be used to control valve  420  so as to control the morphology of a bleb. One of the problems associated with filtering surgery is bleb failure. A bleb can fail due to poor formation or fibrosis. The pressure in the bleb is one factor that determines bleb morphology. Too much pressure can cause a bleb to migrate to an undesirable location or can lead to fibrosis. The pressure of the bleb can be controlled by using the reading from pressure sensor P 2  (at drainage location  410 —in this case, a bleb). In one embodiment of the present invention, the difference between the pressure in the bleb (as measured by P 2 ) and atmospheric pressure (as measured by P 3 ) can be used to control valve  420  to maintain a desired bleb pressure. In this manner, the IOP pressure sensor of the present invention can also be used to properly maintain a bleb. 
     Valve  420  can be controlled by microprocessor  215  or a suitable PID controller. A desired pressure differential (that corresponds to a desired flow rate) can be maintained by controlling the operation of valve  420 . Likewise, a desired IOP, IOP change rate, or bleb pressure can be controlled by controlling the operation of valve  420 . 
     While valve  420  is depicted as a valve, it can be any of a number of different flow control structures that meter, restrict, or permit the flow of aqueous from the anterior chamber  340  to the drainage location  410 . In addition, valve  420  can be located anywhere in or along tube  430 . 
     Finally, there are many other similar uses for the present IOP sensor. For example, various pressure readings can be used to determine if tube  420  is occluded or obstructed in some undesirable manner. As such, failure of a drainage device can be detected. In a self clearing lumen that shunts the anterior chamber  340  to a drainage location  410 , an undesirable blockage can be cleared based on the pressure readings of P 1 , P 2 , and/or P 3 . 
       FIG. 5  is an end cap implementation of an IOP sensor consistent with the principles of the present invention. In  FIG. 5 , pressure sensors P 1  and P 3  are integrated into an end cap  510 . End cap  510  fits in tube  430  so as to form a fluid tight seal. One end of tube  430  resides in the anterior chamber  340 , and the other end of tube  430  (where end cap  510  is located) is located outside of the anterior chamber  340 . Typically, on end of tube  430  resides in the anterior chamber  340 , and the other end resides in the subconjunctival space. In this manner, pressure sensor P 1  is in fluid communication with the anterior chamber  340 . Since there is almost no pressure difference between the anterior chamber  340  and the interior of tube  430  that is in fluid contact with the anterior chamber  340 , pressure sensor P 1  measures the pressure in the anterior chamber  340 . Pressure sensor P 3  is external to the anterior chamber  340  and either measures atmospheric pressure or can be correlated to atmospheric pressure. 
     Typically, tube  430  is placed in the eye to bridge the anterior chamber  340  to the subconjunctival space, as in glaucoma filtration surgery. In this case, P 3  resides in the subconjunctival space. In this configuration, P 3  measures a pressure that is either very close to atmospheric pressure or that can be correlated to atmospheric pressure through the use of a simple function. Since plug  510  provides a fluid tight seal for tube  430 , pressure sensor P 3  is isolated from pressure sensor P 1 . Therefore, an accurate IOP reading can be taken as the difference between the pressure readings of P 1  and P 3  (P 1 -P 3 ). In one embodiment, a single, thin membrane  520 —typically a piezoresistive crystal—resides in the sensor package and is exposed to P 1  on one side (tube side) and P 3  on the other side (isolation side), and thus the net pressure on the membrane  520  is recorded by the sensor, providing a gauge reading corresponding IOP. 
       FIGS. 6A and 6B  are perspective views of the end cap implementation of  FIG. 5 . In this embodiment, pressure sensor P 1  is located on one end of end cap  510  so that it can be located inside tube  430 . Pressure sensor P 3  is located on the other end of end cap  510  so that it can be located outside of tube  430 . A membrane ( 520 ) separates P 1  from P 3 . In this manner, pressure sensor P 1  is isolated from pressure sensor P 3 . While pressure sensors P 1  and P 3  are depicted as being located on opposite surfaces of a membrane  520  in the end cap  510 , they can also be located integral with end cap  510  in any suitable position to facilitate the pressure measurements. 
       FIGS. 7A and 7B  are perspective views of a lumen clearing valve according to the principles of the present invention, which can serve as control valve  420 . In  FIGS. 7A and 7B , the lumen clearing valve  700  includes tube  710 , housing  720 , actuator  730 , actuation arm  740 , tapered arm  750 , pressure sensor P 1 , and pressure sensor P 2 . As previously described with reference to  FIGS. 3 and 4 , one end of tube  710  is located in the anterior chamber and the other end of tube  710  is coupled to housing  720 . Pressure sensor P 1  monitors the pressure in the anterior chamber. Actuator  730  is located in housing  720 . Actuator  730  is coupled to actuation arm  740  which in turn is rigidly connected to tapered arm  750 . Tapered arm  750  is configured to extend into the lumen of tube  710 . Pressure sensor P 2  is located at the outflow region of housing  720  (i.e. in the drainage location). The arrows denote the flow of aqueous from the anterior chamber to the drainage location. 
     Housing  720  is generally flat but may have a slight curvature that accommodates the curvature of the eye. Housing  720  holds actuator  730 . Housing  720  also holds the actuation arm  740  and tapered arm  750 . Tube  710  is fluidly coupled to a channel located in the interior of housing  720 . This channel conducts aqueous from the anterior chamber (through tube  710 ) and to the drainage location. Housing  720  can be made of any of a number of different biocompatible materials such as stainless steel. 
     Actuator  730  moves actuation arm  740  back and forth in a plane. In this manner, actuation arm  740  oscillates or reciprocates when a force is applied on it by actuator  730 . Since tapered arm  750  is rigidly coupled to actuation arm  740 , it also oscillates or reciprocates in tube  710 . Actuator  730  can be based any of a number of different known methods such as electromagnetic actuation, electrostatic actuation, piezoelectric actuation, or actuation by shape memory alloy materials. Actuation arm  740  can be moved by actuator  730  at a low repetition rate (for example, a few Hertz) or a high actuation rate (for example, ultrasonic). 
     Tapered arm  750  is sized to fit in tube  710 . In this manner, tapered arm  750  can be made to oscillate back and forth in tube  710  to clear any material that is blocking tube  710 . Tapered arm  750  has a generally pointed end that is located in tube  710 . As shown, tapered arm  750  also has a larger tapered portion that can serve to restrict flow through tube  710  thus functioning as a valve. In this manner, not only can tapered arm  750  be oscillated to clear material blocking tube  710 , but it can also be moved to a position that partially obstructs flow through tube  710 . The tapered designed of arm  750  allows for a variable level of flow restriction through tube  710  by the varying the position of arm  750  relative to housing  720  and tube  710 . 
     When used as a valve, tapered arm  750  can restrict the amount of aqueous that enters the drainage location and exits the anterior chamber. Controlling aqueous flow can reduce the chances of hypotony after filtration surgery, maintain a suitable IOP, and control the amount of stagnant aqueous in the drainage location. When the drainage location is a subconjunctival bleb, controlling the amount of stagnant aqueous in the bleb can help maintain proper bleb morphology and reduce the amount of fibrosis. Too much stagnant aqueous in a bleb can lead to fibrosis. It has been postulated that fibroblasts form in stagnant aqueous and that too much tension on the bleb wall (i.e. too high a pressure in the bleb) can lead to bleb failure. The use of tapered arm  750  as a valve, therefore, can lead to proper bleb maintenance which decreases the chances of these deleterious side effects. 
     The lumen clearing valve system  700  can be controlled based on readings from P 1 , P 2 , and P 3  as described above. The lumen clearing valve system  700  of the present invention can be made using a MEMS process in which layers are deposited on a substrate that forms part of housing  720 . All of the elements of the lumen clearing valve system  700  can be located on, under, or embedded in a plate that extends into the drainage location—much like currently available glaucoma drainage devices. 
       FIG. 8  is a perspective view of a lumen clearing valve with a fiber clearing member according to the principles of the present invention. The embodiment of  FIG. 8  is similar to that of  FIG. 7 , except that  FIG. 8  also depicts a needle head  810  that is located in the drainage location. Typically, the drainage location is in the subconjunctival space. In this manner, a bleb in the subconjunctival space receives the aqueous that exits the housing  710 . Needle head  810  can be oscillated to keep the bleb clear of fibers or to reduce fibrosis (which is one cause of bleb failure). In this manner, when actuation arm  740  is moved, needle head  810  is moved in the drainage location (in this case, a bleb). Needle head  810  can dislodge fibers and prevent the build up of fibrotic tissue. 
       FIG. 9  is a perspective view of a lumen clearing valve with an aqueous dispersion member to clear fibrosis according to the principles of the present invention. The embodiment of  FIG. 9  is similar to that of  FIG. 7 , except that  FIG. 9  also depicts a needle head  910  that is located in the drainage location. In this embodiment, needle head  910  may serve to clear fibers in the drainage location and/or disperse aqueous to the drainage location. The outlet end of housing  920  is open to allow aqueous to flow to the drainage location. Needle head  910  is located near the outlet within the housing. Needle head  910  is generally broad and blunt so that when it oscillates, aqueous is distributed to the drainage location. Fluid passes from tube  710  to the drainage location via microchannels  930 , which are typically etched into needle head  910 . The dispersion of aqueous can help reduce the formation of resistance at the drainage location, typically created by bleb formation and/or fibrotic growth, by providing a larger effective area in the drainage location, decreasing bleb height, and/or reducing bleb pressure in order to more properly manage bleb morphology. Additionally, the dispersion of aqueous can aid the flow of drainage by providing a mechanical means of overcoming the flow resistance associated with the drainage location, typically created by bleb formation and/or fibrotic growth. 
       FIG. 10  is a perspective view of a lumen clearing valve with hybrid external member according to the principles of the present invention. The embodiment of  FIG. 10  is similar to the embodiment of  FIG. 9 . In  FIG. 10 , a broad needle head  1010  and additional drainage holes  1030  allow for a wide dispersion of aqueous in the drainage location (typically, a subconjunctival bleb). Fluid passes from tube  710  to the drainage location via microchannels  930 , which are typically etched into needle head  1010 . In  FIG. 10 , housing  1020  has a broad outlet end that includes multiple drainage holes  1030 . In addition, the broad end of housing  1020  is open to allow aqueous to flow through this wide opening. Therefore, in the embodiment of  FIG. 10 , aqueous flows from the anterior chamber through tube  710 , through housing  1020  and out of drainage holes  1030  and the broad end of housing  1020  into the drainage location. When needle head  1010  is oscillated, it can serve to clear fibers from the drainage location. It can also disperse aqueous to the drainage location. 
     The embodiments of  FIGS. 7-10  can be operated in two different modes—lumen clearing mode in which the tapered arm  750  oscillates or moves and valve mode in which the tapered arm  750  is maintained in a particular position to restrict fluid flow through tube  710 . In lumen clearing mode, tapered arm  750  is moved or oscillated to clear fibrous material from the interior of tube  710  and/or the drainage location. In lumen clearing mode, tapered arm  750  can also help to disperse aqueous in the drainage location. 
     When operating as a valve, tapered arm  750  can be maintained in a particular position to restrict the flow of aqueous through tube  710 . The position of tapered arm  750  can be changed over time based on pressure readings from pressure sensors P 1 , P 2 , and/or P 3  as described above with respect to  FIGS. 3-6 . In this manner, any of the following can be the basis for control of the tapered arm  750 : IOP, pressure in the bleb, fluid flow rate, etc. 
       FIG. 11A  is a diagram of a two lumen valve and pressure sensor system according to the principles of the present invention. In  FIG. 11A , tube  710  of the active valve/lumen clearing system bridges the anterior chamber and a drainage location. A second tube  430  includes end cap  510  as described in  FIG. 5 . The system of  FIG. 11A  combines the pressure sensor of  FIGS. 5 and 6  with the active valve/lumen clearing device of  FIGS. 7-10 , wherein the latter can serve as control valve  420 . In this manner, one tube ( 430 ) can be used to measure IOP, while a second tube ( 710 ) can be used for draining aqueous. Fluidic communication between a dry location  360  and the P 3  sensing portion of end cap  510  can be provided by tube  1100 .  FIG. 11B  is another possible arrangement, wherein a single tube resides in the anterior chamber  340 . In  FIG. 11B , end cap  510  is located in an opening in tube  430 . 
       FIGS. 12A and 12B  are cross section views of dual tubing that can be used with the system of the present invention. In  FIG. 12A , two lumens,  430  and  710 , are contained in a single tube.  FIG. 12A  shows this dual bore tubing arrangement. In  FIG. 12B , two lumens,  430  and  710 , are contained in two separate tubes that are joined together.  FIG. 12B  shows this dual-line tubing arrangement. Other variations of a dual lumen device can also be used in conjunction with the present invention. 
       FIG. 13  is a perspective view of a two lumen valve and pressure sensor system according to the principles of the present invention. In  FIG. 13 , two tubes,  430  and  710 , are connected at one end (the end that resides in the anterior chamber) and are separated at the other end (in this case, the end that resides in the subconjunctival space). Tube  430  has end cap  510  that measures IOP. Tube  710  receives tapered arm  750 . Tapered arm  750  can serve to clear the interior of tube  710 . Tube  750  can also act as a valve that can partially or totally occlude the interior of tube  710 . Tapered arm  750  is coupled to the any of the systems depicted in  FIGS. 7-10 . A barrier  350  separates P 3  from the outlet of  710 , typically the drainage location  410 . In this manner, P 3  is in a “dry” space  360  and measures an approximation of atmospheric pressure. The outlet end of  710  (shown adjacent to tapered arm  750 ) is located in a “wet” space or drainage location such as  410 . As noted above, P 2  is located in this “wet” space. 
     Power for the pressure monitoring system or active drainage system may be supplied by a power source  205  as described above. As shown in  FIG. 2 , power source  205  is coupled to power generator  1410 . One example of power generator  1410  is shown in  FIG. 14 . In  FIG. 14 , power generator  1410  has a micro-generator  1420  coupled to a rotor  1430 . In this example, as rotor  1430  turns, micro-generator  1420  produces power. As such, the operation of power generator  1410  is much like that of any conventional generator. While rotor  1430  is shown as having four paddles connected to a shaft, any rotor design may be employed. Moreover, any other type of apparatus that converts a fluid flow into power may be employed.  FIG. 14  is intended only as one example. 
     Power generator  1410  is capable of harnessing the aqueous fluid flow from the anterior chamber  340  to the drainage location  410 . Since the general purpose of any glaucoma drainage device is to shunt aqueous from the anterior chamber  340  to a drainage location  410 , aqueous flows from the anterior chamber  340  to the drainage location  410  (in this case, through a tube, such as tube  430 ). There is a natural pressure difference between the fluid pressure in the anterior chamber  340  and the fluid pressure in the drainage location  410 . This pressure difference causes aqueous to flow from the anterior chamber  340  to the drainage location  410 . Power generator  1410  converts this aqueous fluid flow into power. 
     In a typical example, the aqueous flowing through the tube  430  turns rotor  1430  at about 1 revolution per minute based on an aqueous flow rate of about two microliters per minute. If the pressure difference between the anterior chamber  340  and the drainage location  410  is about eight millimeters of mercury, the transferable potential power is about 25 nanowatts (or about two milliJoules of energy) per day. This power can be stored in power source  205  and used to power the systems (pressure sensors, telemetry, active valve, etc.) described in this application. 
       FIG. 15  is an end view of one embodiment of a rotor according to the principles of the present invention. In  FIG. 15 , rotor  1430  has a shaft connected to four paddles. Rotor  1430  is located in tube  430  to harness the fluid flowing through the tube. The arrows denote the direction of aqueous fluid flow through tube  430  and the corresponding direction of rotation of rotor  1430 . As noted,  FIG. 15  depicts one of many possible configurations for rotor  1430 . 
       FIG. 16  is a diagram of one possible location of a power generator in a glaucoma drainage system according to the principles of the present invention. In the example of  FIG. 16 , power generator  1410  is located in or along tube  430 . Tube  430  shunts the anterior chamber  340  to the drainage location  410 . Valve  420  is located at the end of tube  430  as previously described. In this example, the power generated by power generator  1410  is used to power valve  420  (and other components of the system). 
       FIG. 17  is a diagram of another possible location of a power generator in a glaucoma drainage system according to the principles of the present invention. In the example of  FIG. 17 , power generator  1410  is located at the end of tube  430 . Here, power generator  1410  performs two functions: it generates power and it acts as a valve. Since power generator  1410  resists the flow of fluid through tube  430 , this flow resistance can be used to control the rate of aqueous flowing through tube  430 . In other words, power generator  1410  can be operated as an active valve. Moreover, the rotation of the rotor can function to clear the lumen (as described above). 
     In the example of  FIG. 17 , the micro-generator  1420  can be controlled to vary the flow resistance of rotor  1430 . When micro-generator  1420  is a simple magnetic core and coil generator (like the typical electric generator), the distance between the magnetic core and the coil can be varied to vary the force required to turn rotor  1430 . The more force required to turn rotor  1430 , the more resistance to aqueous flowing through tube  430 . Conversely, the less force required to turn rotor  1430 , the less resistance to aqueous flowing through tube  430 . This resistance to aqueous flow can be controlled to maintain a desired IOP. 
     From the above, it may be appreciated that the present invention provides a lumen clearing valve that can be controlled by an IOP sensor. The present invention provides a valve-like device that can clear a lumen, disperse aqueous, and/or clear fibrous material from a drainage location. The present invention also provides an implantable power generator that can be used to power such a system. The present invention is illustrated herein by example, and various modifications may be made by a person of ordinary skill in the art. 
     Other embodiments of the invention will be apparent to those skilled in the art from consideration of the specification and practice of the invention disclosed herein. It is intended that the specification and examples be considered as exemplary only, with a true scope and spirit of the invention being indicated by the following claims.