Patent Application
20150057595
The present disclosure relates generally to valves and associated systems and methods. In some instances, embodiments of the present disclosure are configured to be part of an intraocular pressure (IOP) control system for use in ophthalmic treatments.
Glaucoma, a group of eye diseases affecting the retina and optic nerve, is one of the leading causes of blindness worldwide. Most forms of glaucoma result when the IOP increases to pressures above normal for prolonged periods of time. IOP can increase due to high resistance to the drainage of the aqueous humor relative to its production. Left untreated, an elevated IOP causes irreversible damage to the optic nerve and retinal fibers resulting in a progressive, permanent loss of vision.
One method of treating glaucoma includes implanting a drainage device in a patient's eye. The drainage device allows fluid to flow from the anterior chamber of the eye to a drainage site, relieving pressure in the eye and thus lowering IOP. In order to provide desired treatments to patients, it may be important to regulate the flow of aqueous humor through the drainage device. Some flow regulation devices may be able to measure the pressure within the anterior chamber as well as the pressure at the drainage site of the implant and use these pressure measurements to influence the flow of aqueous humor through the device. However, the actual rate of aqueous flow through these pressure-based flow regulating devices may be unknown. Therefore, it may be desirable to provide flow regulation devices capable of monitoring the actual rate of aqueous flow through the device.
The system and methods disclosed herein overcome one or more of the deficiencies of the prior art.
In one exemplary aspect, this disclosure is directed to an IOP control device for implantation in an eye of a patient, comprising a drainage tube sized for implantation into the eye of a patient, a pressure-driven flow system in fluid communication with the drainage tube, and a flow rate measurement system. In one aspect, the drainage tube includes a drainage lumen in fluid communication with an anterior chamber of the eye. In one aspect, the pressure-driven flow system is in fluid communication with the drainage lumen, and is configured to control the flow of fluid through the drainage tube. In one aspect, the flow rate measurement system is disposed distal to the flow system, and comprises a flow tube, a proximal pressure sensor, and a distal pressure sensor. In one aspect, the flow tube includes a proximal end, a distal end, and a lumen extending therebetween that is configured to be in fluid communication with the drainage lumen. In one aspect, the proximal pressure sensor is disposed proximal of the proximal end, and the distal pressure sensor is disposed distal of the distal end. The flow tube includes a known hydraulic resistance to flow.
In one exemplary aspect, the present disclosure is directed to an IOP control device for implantation in an eye of a patient, comprising a drainage tube, a flow system, a flow rate measurement system, and a controller. The drainage tube is sized for implantation into the eye of a patient. In one aspect, the drainage tube includes a drainage lumen in fluid communication with an anterior chamber of the eye. In one aspect, the flow rate measurement system is disposed distal to the flow system, which is in fluid communication with the drainage lumen. In one aspect, the flow rate measurement system comprises a flow tube, a proximal pressure sensor, and a distal pressure sensor. In one aspect, the flow tube includes a proximal end, a distal end, and a lumen extending therebetween that is configured to be in fluid communication with the drainage lumen. In one aspect, the proximal pressure sensor is disposed at the proximal end, and the distal pressure sensor is disposed at the distal end. The flow tube includes a known hydraulic resistance to flow. In one aspect, the controller is configured to receive data from the proximal pressure sensor and data from the distal pressure sensor, and is configured to determine flow rate based on the data from the proximal pressure sensor, the data from the distal pressure sensor, and pre-stored information relating to the hydraulic resistance to flow.
In another exemplary embodiment, the present disclosure is directed to a method of monitoring flow rate of fluid from an anterior chamber of an eye through an implantable device. The method comprises directing fluid through a drainage tube containing a flow measurement system and a flow system configured to control the flow of fluid from the anterior chamber through the drainage tube to a drainage site. In one aspect, the flow measurement system comprises a flow tube having a known hydraulic resistance to flow, a proximal pressure sensor disposed between the flow system and the flow tube, and a distal pressure sensor disposed between the flow tube and the drainage site. The method further comprises measuring a first pressure proximal to the flow tube using the proximal pressure sensor, measuring a second pressure distal to the flow tube using the distal pressure sensor, and calculating the flow rate through the drainage tube using the known hydraulic resistance to flow of the flow tube, the first pressure, and the second pressure.
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.
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.
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 a flow rate measurement system to monitor the rate of fluid flow though a flow passageway or tube. In some instances, embodiments of the present disclosure are configured to be part of an IOP control system. In some instances, embodiments of the present disclosure are configured to be disposed within or carried onboard an implantable glaucoma drainage device. In some instances, embodiments of the present disclosure are configured to be used in the operation of pressure-driven membrane valves within an implantable glaucoma drainage device. The flow rate measurement system disclosed herein calculates the flow rate through a flow passageway including at least a portion having a known hydraulic resistance by measuring pressures upstream and downstream of this portion.
Thus, an IOP control system utilizing the flow rate measurement system disclosed herein enables the real-time measurement of the aqueous flow rate through an implanted drainage device, which may facilitate better monitoring and treatment of the disease (e.g., glaucoma) than IOP control systems that operate based on pressure measurements alone. The flow rate measurement systems disclosed herein may guide treatment regimens in response to changes in the aqueous humor outflow rate. For example, in at least one embodiment, knowledge of the real-time flow rate of aqueous humor through the drainage device enables the user and/or the IOP control system to change the pumping schedule of the drainage device in order to better regulate aqueous outflow from the anterior chamber through the drainage device. Those of skill in the art will realize that the flow rate measurement system disclosed herein may be utilized in alternative applications requiring flow rate measurement through a flow passageway.
When implanted, the plate 182 may be located in the subconjunctival pocket between the conjunctiva and sclera. It may be generally located on an ocular quadrant commonly used for conventional glaucoma drainage devices with plates; that is, it may be centered such that it is located between the neighboring ocular muscles that define the ocular quadrant chosen for implantation. In the pictured embodiment, the plate 182 is configured to fit at least partially within the subconjunctival space and is sized for example within a range between about 15 mm×10 mm to about 30 mm×15 mm. In some embodiments, the plate 182 has a thickness less than about 2 mm thick. For example, in one embodiment, the plate has a thickness of about 1 mm thick. The plate 182 may be curved to approximate the radius of the eye globe. In some embodiments, the plate 182 is rigid and preformed with a curvature suitable to substantially conform to the globe or it may be flexible to conform to the globe. The above dimensions and arrangement are exemplary only, and other sizes and arrangements are contemplated.
The drainage tube 184 is sized to extend from the plate 182 to the anterior chamber of the eye. The drainage tube 184 bridges the anterior chamber and the plate 182 in the subconjunctival pocket to provide an auxiliary flow path for aqueous humor, bypassing the flow-resistive conventional pathway through the trabecular meshwork and shunting aqueous humor directly to a drainage site. In the example shown, the drainage tube 184 is a single tube having a single lumen. Other embodiments include a plurality of drainage tubes or a plurality of lumens cooperating together to permit fluid to flow through the implantable system 180. Aqueous humor may drain through the drainage tube from the anterior chamber to and out of the plate 182 to alleviate elevated intraocular pressure conditions.
The power source 205, which provides power to the system 200, is typically a rechargeable battery, such as a lithium ion or lithium polymer battery, although other types of batteries may be employed. In other embodiments, any other type of power cell is appropriate for the power source 205. The power source can be recharged via inductive coupling such as an RFID link or other type of electromagnetic coupling.
The processor 215 is typically an integrated circuit with power, input, and output pins capable of performing logic functions. For example, the processor 215 may perform logic functions based on inputs from the IOP sensor system 210 and/or the flow rate measurement system 235 to determine the current IOP of the eye, the flow rate through the implantable system 180 (shown in
The processor 215 may include one or more programmable processor units running programmable code instructions for modulating flow through the flow system 230, among other functions. The processor 215 may be integrated within a computer and/or other processor-based devices suitable for a variety of ocular applications. In some embodiments, the processor 215 regulates flow through the flow system 230 based on a programmable regimen, which may be carried by such a device and/or the memory 220. In some instances, the programmable regimen includes specific command signals to the flow system 230 based on different input data from the IOP sensor system 210 and/or the flow rate measurement system 235. In some embodiments, the processor 215 can receive input data from the IOP sensor system 210 and/or the flow rate measurement system 235 via wireless or wired mechanisms. The processor 215 may use such input data to generate control signals to control or direct the operation of the flow system 230 and thereby affect the rate of fluid flow from the anterior chamber. In some embodiments, the processor 215 is offboard the plate 182 and is in direct wireless communication with the IOP sensor system 210, the flow rate measurement system 235, and/or the flow system 230, and can receive data from and send commands to these component parts of the IOP control system 200.
The memory 220, which is typically a semiconductor memory such as RAM, FRAM, or flash memory, interfaces with the processor 215. As such, the processor 215 can write to and read from the memory 220, and perform other common functions associated with managing semiconductor memory. In this manner, a series of flow rate calculations, command algorithms, and/or pressure readings can be stored in the memory 220.
The processor 215 and/or the memory 220 may also include software containing one or more algorithms or programmable regimens defining one or more functions or relationships between command signals and input data (e.g., input data received from the flow rate measurement system 235). The algorithm may dictate command signals to the flow system 230 depending on the received input data or mathematical derivatives thereof.
The data transmission module 225 may employ any of a number of different types of data transmission. For example, in various embodiments, the data transmission module 225 may be an active device such as a radio or a passive device with an antenna capable of wireless transmission. Alternatively, the data transmission module 225 may be activated to communicate an elevated IOP condition or a real-time flow rate to a secondary device such as a PDA, cell phone, computer, wrist watch, custom device for this purpose, remote accessible data storage site (e.g. an internet server, email server, text message server), or other electronic device or service. Additionally, the data transmission module 225 may be utilized to program or reprogram the device with alternate treatment/control schedules.
In
In some embodiments, the pressure sensor P1 is located in a lumen or tube that is in fluid communication with the anterior chamber, such as the drainage tube 330. In the embodiment shown, the pressure sensor P1 measures the pressure in the tube 330 upstream from the flow system 230 and downstream from the anterior chamber 300. In this manner, pressure sensor P1 measures the pressure in the anterior chamber 300 because the expected measurement discrepancy between the true anterior chamber pressure and that measured by P1 when located in a tube downstream of the anterior chamber (even when located between the sclera and the conjunctiva) is very minimal.
In some embodiments, the system includes barriers that separate the sensors P1, P2, P3, and P4. These barriers may be elements of the system itself. For example, in
Generally, IOP is a gauge pressure reading—the difference between the absolute pressure in the eye (as measured by P1) and atmospheric pressure (as measured by P3). In one embodiment of the present disclosure, pressure readings are taken by the pressure sensors P1 and P3 simultaneously or nearly simultaneously over time so that the actual IOP can be calculated (as P1-P3 or P1−f(P3), where f(P3) indicates a function of P3). The pressure readings of P1 and P3 can be stored in memory 220 by the processor 215. They can later be read from memory so that actual IOP over time can be interpreted by a physician.
The pressure sensor P4 may be located in a pocket at the drainage site 360, such as a bleb, that generally contains aqueous humor or in communication with such a pocket, via a tube for example, and is in the drainage site 360. The drainage site 360 may be, by way of non-limiting example, in a subconjunctival space, a suprachoroidal space, a subscleral space, a supraciliary space, Schlemm's canal, a collector channel, an episcleral vein, and a uveo-scleral pathway, among other locations in the eye. The difference between the readings taken by the pressure sensor P1 and the pressure sensor P4 (P1-P4) provides an indication of the pressure differential between the anterior chamber 300 and the drainage site 360. In one embodiment, this pressure differential dictates the rate of aqueous humor flow from the anterior chamber 300 to the drainage site 360.
In
The pressure sensors P5 and P6 flank the entrance and exit of the flow tube 400. In particular, the pressure sensor P5 is located proximal to the flow tube 400, and the pressure sensor P6 is located distal to the flow tube 400. The flow tube 400 and the pressure sensors P5 and P6 are arranged and configured relative to the drainage tube 330 to allow aqueous humor from the flow system 230 to flow from the drainage tube 330, past the proximal pressure sensor P5, through the lumen 405 of the flow tube 400 from the proximal end 410 to the distal end 415, and past the distal pressure sensor P6 toward the drainage site 360. Aqueous humor exits the flow tube 400 at the distal end 415 to pass the pressure sensor P6 for release at the drainage site 360. In the pictured embodiment, the pressure sensors P5 and P6 are disposed immediately adjacent the proximal end 410 and the distal end 415, respectively, of the flow tube 400. Thus, the proximal pressure sensor P5 measures the pressure in the flow path within the drainage tube 330 immediately before the proximal end 410 of the flow tube 400, and the distal pressure sensor P6 measures the pressure in the flow path within the drainage tube 330 immediately after the distal end 415 of the flow tube 400. In other embodiments, any one or both of the pressure sensors P5 and P6 are located a distance apart from the flow tube 400. In some embodiments, any one or both of the pressure sensors P5 and P6 are located within the flow tube 400 near or at the proximal end 410 and the distal end 415, respectively, of the flow tube 400.
The pressure sensors P1, P2, P3, P4, P5, and P6 can be any type of pressure sensors 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. In other embodiments, the flow rate measurement system 235 may include more than two pressure sensors. For example, in one embodiment, the flow rate measurement system 235 may include two proximal pressure sensors P5 and/or two distal pressure sensors P6 disposed within the drainage tube 330 at different positions relative to the flow tube 400. In other embodiments, a differential pressure sensor may be used to measure the difference across lumen 405, representing the difference between P5 and P6.
The flow system 230 is configured to control the flow of drainage fluid through the drainage tube 330, and thereby control pressure in the eye, including the IOP. The flow system 230 is configured to selectively allow or block the flow of aqueous humor flowing from the anterior chamber 300 through the drainage tube 330 and the flow tube 400 to the drainage site 360. The flow system 230 may include any number and combination of flow control structures such as, by way of non-limiting example, valves, pumps, and/or check valves before entering the drainage site. For example, in some embodiments, the flow system 230 comprises a series of valves. In other embodiments, the flow system 230 comprises a pump. In some embodiments, the flow system 230 comprises a combination of valves and pumps. Some examples of valves that comprise the flow system 230 include membrane valves, check valves, reed valves, pressure relief valves, and other types of valves. It is worth noting that for biocompatibility, the devices disclosed herein may be coated or encapsulated in a material such as polypropylene, silicon, Parylene, or other materials.
A desired pressure differential can be maintained by monitoring and controlling the flow rate through the flow system 230. For example, when IOP is high and/or the flow rate through the drainage tube 330 is low, the flow system 230 may operate to permit increased flow through the drainage tube 330, and when IOP is low and/or the flow rate through the drainage tube 330 is elevated, the flow system 230 may operate to decrease the flow through the drainage tube 330. Likewise, some embodiments of the flow rate measurement system 235 are configured to monitor the flow rate of drainage fluid to the drainage site 360 or bleb, and thereby enable the user and/or processor 215 to control the bleb pressure to maintain a desired fluid flow to the bleb and thereby decrease fibrosis and increase absorption efficiency. To accomplish this, the flow rate measurement system 235 may convey pressure measurements sensed by the pressure sensors P5 and P6 to the processor 215, and the processor 215 may utilize that data to select a control algorithm and/or send particular command signals to the flow system 230 to appropriately adjust the flow rate through the drainage tube 330. In some embodiments, the flow system 230 may also be responsive to instructions from the processor 215 based on input data received from the pressure sensors P5 and P6, the known resistance of the flow tube 400, and the calculated flow rate. The pressure readings of P5 and P6 as well as the calculated flow rates over time may be stored in memory 220 by the processor 215. They can later be read from memory so that actual flow rates over time can be interpreted by a physician. With the flow rate data and IOP values, it is then possible to determine if the bleb is still viable or if some form of surgical intervention is required to improve outflow performance. In some embodiments, the flow system 230 may be responsive to instructions from the processor 215 based on input data received from the pressure sensors P1, P2, P3, and/or P4, and the calculated IOP. In some embodiments, the flow system 230 may be responsive to instructions from the processor 215 based on a pre-programmed treatment protocol or input data received from the IOP sensor system as well as the flow rate measurement system 235.
The IOP control system 200 is configured to adjust the flow through the flow system 230 based on measured pressure values or derivatives from the pressure sensors P5 and P6 of the flow rate measurement system 235. After the implantable portion of the IOP control system 200 is implanted within the eye of a patient (e.g., a drainage device including the drainage tube 330, the flow system 230, and the flow rate measurement system 235), the flow rate measurement system 235 may communicate real time measured pressures from the proximal pressure sensor P5 and the distal pressure sensor P6 to the processor 215 (i.e., at a time T1). The processor 215 calculates the real time flow rate through the drainage tube 330 based on known mathematical principles of flow rate based on the pressure drop across a fluid conduit having a known resistance to flow. For example, in at least one embodiment, the processor 215 calculates the flow rate through the flow tube 400 and the drainage tube 330 by employing the equation Q=ΔP/R, where Q is the flow rate, ΔP is the pressure drop across the flow tube 400 (e.g., P5-P6), and R is the known hydraulic resistance of the flow tube 400.
If the processor 215 determines that the flow rate is not within a desired range, the IOP control system 200 may adjust the flow system 230 to increase or decrease drainage flow through the drainage tube 330 to effect a flow rate change to a desired flow rate (and may thereby effect a pressure change to the desired IOP). To do this, the processor 215 operates the flow system 230 with the power source 205 to change the flow rate through the flow system 230. After adjusting flow through the flow system 230, the flow rate measurement system 235 can again measure and communicate real time measured pressures from the proximal pressure sensor P5 and the distal pressure sensor P6 to the processor 215 (i.e., at a time T2 later than the time T1). The processor 215 can calculate this second flow rate using the same mathematical principles described above to reevaluate the flow through the drainage tube 330 and appropriately adjust the flow through the flow system 230 based on the calculated flow rate. In some embodiments, the processor 215 also evaluates pressure readings from the IOP sensor system 210 and calculations thereof before adjusting the operation of the flow system 230.
The devices, systems, and methods described herein achieve IOP control using a relatively small and inexpensive flow rate measurement system disposed on an implantable drainage device. In some embodiments, the exemplary IOP control system disclosed herein uses data from the flow rate measurement system as well as an IOP sensor system to affect drainage flow, thereby taking into account intraocular pressure and/or bleb pressures to affect drainage flow through the drainage tube. In other embodiments, the IOP control system disclosed herein may lack an IOP sensor system and operate to affect flow through the drainage tube based mainly on pressure data from the flow rate measurement system.
In particular, the flow rate measurement system disclosed herein enables IOP control systems to better monitor the disease state (e.g., glaucoma progression) and to more effectively guide treatment regimens (e.g., pumping schedules) in response to changes in aqueous humor outflow rate through the implanted drainage device. Use of the flow rate measurement system disclosed herein in the IOP control system enables the use of better control algorithms that are able to take into account the actual, real time flow rate of aqueous humor through the drainage device as opposed to being based on raw pressure measurements alone.
In addition, the simple design of the flow measurement system may result in a thinner implant that will likely be more comfortable for the patient. In addition, because the flow tube of the flow measurement system may be fabricated as an integral part of the drainage tube, the overall manufacturing process may be simplified and costs may be reduced.
Embodiments in accordance with the present disclosure may be used in a variety of applications to monitor flow and/or pressure. For example, but not by way of limitation, embodiments of the present disclosure may be utilized to monitor flow rates in a flow control system as part of a dialysis system, a process control system, and/or a drug delivery system. Some embodiments of the present disclosure may be utilized to monitor flow rates in a variety of fluid flow implants such as, but not by way of limitation, the urinary tract, the brain (e.g., to regulate intracranial pressure), and the circulatory/renal system (e.g., as part of a dialysis system).
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.
