System and method for diagphragm pumping using heating element

Systems and methods for treating an ocular condition includes a heating chamber comprising a material expandable when heated and comprising a flow passage having an inlet and an outlet. A heating element is arranged and disposed to introduce heat in the heating chamber. A flexible diaphragm separates the heating chamber from the flow passage, and is moveable between a first position and a second position to change a volume of one of the pump chamber and flow passages in response to a temperature change in the heating chamber.

BACKGROUND

The present disclosure relates generally to pressure/flow control systems and methods for use in treating a medical condition. In some instances, embodiments of the present disclosure are configured to be part of an IOP control system for the treatment of ophthalmic conditions.

Glaucoma, a group of eye diseases affecting the retina and optic nerve, is one of the leading causes of blindness worldwide. The chamber pressure of the eye is known as intraocular pressure (IOP). Most forms of glaucoma result when 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. This may be due to a direct effect of the raised pressure upon the optic nerves and/or the effect of chronic under-perfusion of the nerve head.

The eye's ciliary body continuously produces aqueous humor, the clear fluid that fills the anterior segment of the eye (the space between the cornea and lens). The aqueous humor flows out of the anterior chamber (the space between the cornea and iris) through the canalicular and the uveoscleral pathways, both of which contribute to the aqueous drainage system. The orbital globe of the eye is an essentially non-compliant sphere, allowing IOP to be influenced by a change in volume of the contents of the orbit, including both the anterior segment and the posterior segment. Thus, the delicate balance between the production and drainage of aqueous humor can influence the IOP of the eye.

FIG. 1is a diagram of the front portion of an eye10that helps to explain the processes of glaucoma. InFIG. 1, representations of the lens110, cornea120, iris130, ciliary body140, trabecular meshwork150, Schlemm's canal160, the anterior segment165including both the anterior chamber170and the posterior chamber175, the posterior segment178, the sclera180, the retina182, the choroid185, the limbus190, the suspensory ligaments or zonules195, the suprachoroidal space200, and the conjunctiva202are pictured. Aqueous fluid is produced by the ciliary body140, which lies beneath the iris130and adjacent to the lens110in the anterior chamber170of the anterior segment of the eye165. This aqueous humor washes over the lens110and iris130and flows to the drainage system located in the angle of the anterior chamber170. The posterior segment178is filled with a gel-like substance called vitreous humor. Normal regulation of IOP occurs chiefly through the regulation of the volume of aqueous humor. Similarly, however, changes in the volume of fluid (e.g., vitreous humor) within the posterior segment can affect IOP.

After production by the ciliary body140, the aqueous humor may leave the eye by several different routes. Some goes posteriorly through the vitreous body behind the lens110to the retina, while most circulates in the anterior segment of the eye to nourish avascular structures such as the lens110and the cornea120before outflowing by two major routes: the conventional outflow pathway route205and the uveoscleral outflow route210. The angle of the anterior chamber170, which extends circumferentially around the eye, contains structures that allow the aqueous humor to drain. The conventional outflow pathway (or trabecular meshwork) route is the main mechanism of outflow, accounting for a large percentage of aqueous egress. The route extends from the anterior chamber angle (formed by the iris130and the cornea120), through the trabecular meshwork150, into Schlemm's canal160. The trabecular meshwork150, which extends circumferentially around the anterior chamber170, is commonly implicated in glaucoma. The trabecular meshwork150seems to act as a filter, limiting the outflow of aqueous humor and providing a back pressure that directly relates to IOP. Schlemm's canal160is located just peripheral to the trabecular meshwork150. Schlemm's canal160is fluidically coupled to collector channels (not shown) allowing aqueous humor to flow out of the anterior chamber170. The arrows205show the flow of aqueous humor from the ciliary bodies140, over the lens110, over the iris130, through the trabecular meshwork150, and into Schlemm's canal160and its collector channels (to eventually reunite with the bloodstream in the episcleral vessels (not shown)).

The uveosceral route210accounts for the major remainder of aqueous egress in a normal eye, and also begins in the anterior chamber angle. Though the anatomy of the uveoscleral route210is less clear, aqueous is likely absorbed by portions of the peripheral iris130, and the ciliary body140, after which it passes into the suprachoroidal space200. The suprachoroidal space200is a potential space of loose connective tissue between the sclera180and the choroid185that provides a pathway for uveoscleral outflow. Aqueous exits the eye along the length of the suprachoroidal space to eventually reunite with the bloodstream in the episcleral vessels.

One method of treating glaucoma includes implanting a drainage device in a patient's eye. The drainage device allows fluid to flow from the interior of the eye (e.g., from the posterior segment to a drainage site, relieving pressure in the eye and thus lowering IOP). The system and methods disclosed herein overcome one or more of the deficiencies of the prior art.

SUMMARY

According to an exemplary aspect, the present disclosure is directed to a system for treating an ocular condition including a heating chamber comprising a material expandable when heated and comprising a flow passage having an inlet and an outlet. A heating element is arranged and disposed to introduce heat in the heating chamber. A flexible diaphragm separates the heating chamber from the flow passage, and is moveable between a first position and a second position to change a volume of one of the pump chamber and flow passages in response to a temperature change in the heating chamber.

In an aspect, the heating element is a resistive heating element configured to increase in temperature when a current is passed therethrough. In an aspect, the heating element is disposed within the pump chamber. In an aspect, the heating element is a resistive heating element disposed along a wall of the heating chamber opposite the flexible diaphragm. In an aspect, the system includes a power source and a feed wire extending on opposing sides of the heating element, the feed wire being in electrical communication with the power source. In an aspect, the system includes at least one sensor arranged to detect a pressure indicative of intraocular pressure. In an aspect, the system includes a processor configured to operate the heating element based on information detected by the at least one sensor. In an aspect, the system includes a first one-way valve and a second one-way valve operable as the flexible diaphragm moves from the first position to the second position and back to the first position to promote the passage of drainage fluid through the flow passage in one direction. In an aspect, the first and second check valves are reed valves or flapper valves.

According to another exemplary aspect, the present disclosure is directed to a system implantable in an eye for treating an ocular condition. The system includes a housing sized for implantation in an eye of a patient, comprising: a sealed heating chamber; and a fluid flow passage having an inlet and an outlet. The system also includes a flexible diaphragm carried by the housing and disposed between and separating the heating chamber from the fluid flow passage and includes a heating element arranged and disposed to induce heat in the heating chamber to change pressure in the chamber. A power source may be in electrical communication with the heating element and configured to induce electrical current in the heating element.

In another exemplary aspect, the present disclosure is directed to a method for treating an ocular condition comprising: inducing flow of a liquid through a flow pump having a flexible diaphragm separating a flow passage from a heating chamber; moving the flexible diaphragm from a first position to a second position by increasing a temperature of a fluid in the heating chamber; forcing fluid from the flow passage as the flexible diaphragm moves the first position to the second position; and drawing fluid into the flow passage by moving the flexible diaphragm from the second position to the first position.

In an aspect, moving the flexible diaphragm by increasing a temperature of a fluid in the heating chamber comprises applying voltage to a heating element disposed in a closed chamber. In an aspect, the method includes drawing fluid into the flow passage through a first one-way valve and pushing fluid out of the flow passage through a second one-way valve. In an aspect, the method includes implanting the flow pump in an eye of a patient.

DETAILED DESCRIPTION

The present disclosure is directed to a flow control system for treating a medical condition, such as glaucoma, by using a heat generating resistive element within an intraocular implant to create a pumping action usable to transfer or pump fluid. In one aspect, the system may use this pumping action to adjust IOP by regulating fluid drainage through the intraocular implant, such as a glaucoma drainage device (GDD). Since the system employs a diaphragm that flexes in cycles and cooperates with check valves to generate pumping action, the system may be actuated and may recover more quickly than other types of pump systems, such as those using electrolysis to create air bubbles. Thus, the flow control systems and methods disclosed herein allow the flow control system to pump aqueous solutions to control IOP while maintaining responsiveness unachieved in traditional GDDs.

FIG. 2is a schematic diagram of an exemplary drainage device or implant300positioned within an eye of a patient. The drainage implant300is designed to regulate IOP by utilizing an adjustable smart valve or active element (e.g., without limitation, a pump) to throttle or pump fluid out of a posterior segment178into a drainage site.

In the embodiment pictured inFIG. 2, the implant300is arranged in the eye such that three areas of pressure interact with the implant: P1, P2, and P3. Pressure area P1reflects the pressure of the posterior segment178, pressure area P2reflects the pressure of a drainage site320, and pressure area P3reflects a pressure located remotely from P1and P2(effectively reflecting atmospheric pressure). In some embodiments, pressure area P1reflects the pressure located in a lumen or tube that is in fluidic communication with the posterior segment178.

InFIG. 2, the implant300includes a drainage tube305and a divider310associated with a flow controller315. The drainage tube305drains fluid from the posterior segment178of the eye to the drainage location320, which may be the suprachoroidal space200shown inFIG. 1. Other examples of a drainage location320include, but are not limited to: a subconjunctival space, a subscleral space, a supraciliary space, an episcleral vein, and other uveoscleral pathways. The drainage tube305includes an inlet tube or inlet tube portion325, which extends from the posterior segment178to the flow controller315, and an outlet tube or outlet tube portion330, which extends from the flow controller315to the drainage site320. The inlet tube325includes a proximal end332coupled to the flow controller315and a distal end334positioned within the posterior segment178. The outlet tube330includes a proximal end335coupled to the flow controller315and a distal end340positioned within the drainage site320.

The flow controller315regulates IOP by controlling, such as by throttling or inducing the flow of fluid, through the tube305, from the inlet tube325to the outlet tube330. In some instances, the flow controller315throttles the flow of fluid through the tube305as a function of a pressure differential. The flow controller315may include components or elements, such as valves, pumps or others, described further below with reference toFIG. 3, that control pressure by regulating the amount of drainage flow through the implant300. The flow controller315may include any number of valves and any number of pumps, or may not include a pump or may not include a valve. In some embodiments, the flow controller315is an active system that is responsive to signals from a processor to increase flow, decrease flow, or to maintain a steady flow as a function of pressure differentials at pressure areas P1, P2, and P3. In one embodiment, it does this by actuating a pump to increase or decrease the fluid flow passage through the flow controller315.

In addition, the flow controller315may incorporate pressure sensors to monitor and utilize the pressures P1, P2, and P3to achieve a desired IOP. In some embodiments, the implant300responds to the pressure differentials between the pressures sensed at P1, P2, and P3by sensors S1, S2, and S3, respectively, to control the flow controller315and thereby throttle the flow rate of fluid through the drainage tube305to control IOP. In some embodiments, the various pressure differentials across the pressure areas sensed at P1, P2, and P3(P1-P2, P1-P3, P2-P3) drive the flow controller315and dictate the valve position or pump state to throttle the flow rate of fluid through the drainage tube305to control IOP. In some embodiments, the implant may include only a pressure sensor S1, and may be coupled with a separate drainage device that includes the remaining sensors S2and S3. Such a separate drainage device may lack a drainage tube305and/or a flow controller315.

In the embodiment shown, a pressure sensor S1measures the pressure in the tube305upstream from the flow controller315and downstream from the posterior segment178. In this manner, the pressure sensor S1measures the pressure in the posterior segment178. The expected measurement discrepancy between the true posterior segment pressure and that measured by S1when located in a tube downstream of the posterior segment (even when located between the sclera and the conjunctiva) may be negligible.

A pressure sensor S2is located at the drainage site320or in fluid communication with the drainage site320via the outlet tube320. As such, the pressure sensor S2may be located in the subconjunctival space, suprachoroidal space200, a subscleral space, a supraciliary space, an episcleral vein, or another uveoscleral pathway, for example.

In some embodiments, the divider310acts as a barrier that separates the pressure region measured by the pressure sensor S3from the pressure region measured by the pressure sensor S2. In some embodiments, the system includes other barriers that separate the sensors S1, S2, and S3. These barriers may be elements of the flow controller315itself. InFIG. 2, the pressure region measured by the pressure sensor S3is physically separated from the pressure region measured by the pressure sensor S2by the divider310. The divider310is a physical structure that separates the drainage area306from the isolated location of pressure region measured by the pressure sensor S3. The divider310may be sutured and/or healed tissue.

Generally, IOP is a gauge pressure reading—the difference between the absolute pressure in the eye (as measured by sensor S1) and atmospheric pressure (as measured by sensor S3). Atmospheric pressure, typically about 760 mmHg, often varies in magnitude by 10 mmHg or more depending on weather conditions or indoor climate control systems or elevation changes. In addition, the effective atmospheric pressure can vary significantly—in excess of 300 mmHg—if a patient goes swimming, hiking, riding in an airplane, etc. Such a variation in atmospheric pressure is significant since IOP is typically in the range of about 15 mmHg. Thus, for accurate monitoring of IOP, it is desirable to have pressure readings for the interior chamber of the eye (as measured by sensor S1) and atmospheric pressure in the vicinity of the eye (as measured by sensor S3).

In one embodiment of the present invention, pressure readings are taken by the pressure sensors S1and S3simultaneously or nearly simultaneously over time so that the actual IOP can be calculated (as S1-S3or S1-f(S3), where f(S3) indicates a function of S3). In another embodiment of the present invention, pressure readings taken by the pressure sensors S1, S2, and S3can be used to control a device that drains aqueous from the posterior segment178. For example, in some instances, the implant300reacts to the pressure differential across S1and S3continuously or nearly continuously so that the actual IOP (as S1-S3or S1-f(S3)) can be responded to accordingly.

The drainage implant300may be shaped and configured to be implanted within the subconjunctival space, between the conjunctiva202and the sclera180. In some embodiments, the bulk of the implant300may be positioned within the eye in a subconjunctival space between the conjunctiva202and the sclera180with the flow controller315positioned such that the implant does not come into contact with the optic nerve. For example, in one embodiment, depending upon the size and shape of the implant, the implant300may be positioned approximately 8 to 10 mm posterior to the limbus190(the border between the cornea and the sclera). The drainage implant300may be held in place within the eye via anchoring sutures, the angle of implantation and surrounding anatomy, or by a spring force or other mechanisms that stabilize the implant300relative to the patient's eye. In some embodiments, the inlet tube325and the outlet tube330are coupled to the flow controller315at the location of the subconjunctival space, and extend from the subconjunctival space into the posterior segment178and the delivery site, respectively.

FIG. 3is a block diagram of an exemplary flow controller315forming a part of an implant implantable in an eye of a patient for the treatment of glaucoma or other conditions. The flow controller315is configured in a manner that provides IOP pressure control, but may also regulate and control bleb pressures, reducing complications arising from surgical implant glaucoma treatments. InFIG. 3, the flow controller315includes a power source350, a processor355, a memory360, a data transmission module365, and a flow system370.

The power source350is 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 source350. Power source350provides power to the flow controller315, and more particularly to processor355. Power source can be recharged via an RFID link or other type of magnetic coupling.

Processor355is typically an integrated circuit with power, input, and output pins capable of performing logic functions. In various embodiments, processor355is a targeted device controller. In such a case, processor355performs specific control functions targeted to a specific device or component, such as a data transmission module365, power source350, flow system370, or memory360. In other embodiments, processor355is a microprocessor. In such a case, processor355is programmable so that it can function to control more than one component of the device. In other cases, processor355is not a programmable microprocessor, but instead is a special purpose controller configured to control different components that perform different functions.

Memory360is typically a semiconductor memory such as NAND flash memory. As the size of semiconductor memory is very small, and the memory needs of the implant300are small, memory360occupies a very small footprint of the flow controller315. Memory360interfaces with processor355. As such, processor355can write to and read from memory360. For example, processor355can be configured to receive data as signals from the sensors S1, S2, and S3(FIG. 2) and write data to memory360. In this manner, a series of measurements that may be indicative of IOP readings can be stored in memory360. Processor355is also capable of performing other basic memory functions, such as erasing or overwriting memory360, detecting when memory360is full, and other common functions associated with managing semiconductor memory.

Data transmission module365may employ any of a number of different types of data transmission. For example, data transmission module365may be an active device such as a radio. Data transmission module365may also be a passive device such as the antenna on an RFID tag. In this case, an RFID tag includes memory360and data transmission module365in the form of an antenna. An RFID reader can then be placed near the implant300to write data to or read data from memory360. Since the amount of data typically stored in memory360is 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 memory360and transmitted by data transmission module365include, 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.

Alternatively, data transmission module365may 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. For example, in a hospital setting, after a patient has undergone glaucoma surgery and had implant300implanted, a secondary device may be located next to the patient'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), processor355can read IOP measurements made by the sensors S1, S2, and S3. If processor355determines that an unsafe IOP condition exists, data transmission module365can alert the patient and medical staff directly or by transmitting the unsafe readings to a secondary device.

The flow system370is the physical structure used to control the flow of fluid through the flow controller315. It may include, for example, one or more pump mechanisms, valves, or other elements that help regulate the flow of fluid through the implant.

FIGS. 4A and 4Bshow an exemplary flow system370that may be used in the implant300, connected to the inlet tube325and the outlet tube330. The flow system370includes a flexible diaphragm588shown inFIG. 4Abiased inward and shown inFIG. 4Bbiased outward. The flexible diaphragm588may be, for example, a Parylene or glass membrane, and may have a thickness ranging from 1 to 15 μm, although thicker and thinner diaphragms are contemplated. In the exemplary embodiment shown, the flow system370includes an upper housing570forming a part of a heating chamber580, a lower housing571forming a part of a flow passage590, an entrance port572in communication with the flow passage590, and an exit port574in communication with the flow passage590. The flexible diaphragm588is disposed between and separates the heating chamber580from the flow passage590. Here, the entrance port572is in fluid communication with the inlet tube325, and the exit port574is in fluid communication with the outlet tube330. In some embodiments the outlet tube330is not present in the flow system370, and the exit port574exits directly to the drainage site, which may include a bleb.

The upper and lower housings570,571, along with other aspects of the implant300and flow system370may be formed using MEMS (Micro-Electro-Mechanical Systems) technology.

In this embodiment, the flow system370is a pump576formed by the flexible diaphragm188, a one-way check valve592adjacent the exit port574, and a one-way check valve594adjacent the entrance port572. Here, the check valves592,594are formed of deformable cantilevers that prevent backflow. This ensures that drainage fluid travels one direction from the posterior segment of the eye toward the drainage site. It also ensures that fluid at the bleb does not reenter the flow system370. Other embodiments include other types of check valves, such as ball valves, spring valves, reed valves, and others. Some embodiments include tapered openings at the flow passage entrance that decreases in cross-sectional area (according to flow direction) and the check valve592at the flow passage exit may include a narrow opening that increases in cross-sectional area. Accordingly, because of the shape of the openings, fluid flow will tend to flow easier out the exit port than out the entrance port—even in the absence of any movable parts such as flapper or reed valves.

Within the heating chamber580, the flow system315includes an actuator fluid582that may be a liquid or gas, and a heating element584. In some embodiments, the heating element584may be disposed adjacent the flexible diaphragm588, and in some embodiments, may be in contact with the flexible diaphragm588to provide heat to the flow system315. In the embodiment shown, the heating element is disposed adjacent the housing permitting the flexible diaphragm to flex without being inhibited by the possibly more rigid heating element. The heating element584can be powered by the power source under the control of the processor355.

FIG. 5shows a bottom view of the flexible diaphragm588and the heating element584on the upper housing570, taken along lines5-5inFIG. 4A. With reference toFIGS. 4A, 4B, and 5, the flexible diaphragm588is disposed over the upper housing570, which has a circular void that forms the heating chamber580. The diaphragm588may deflect into or out of the heating chamber580, as is apparent inFIGS. 4A and 4B. The resistive heating element584extends across the heating chamber580, and is in electrical connection with feed wires596that extend beyond the heating chamber580and diaphragm588to connect to the power source350.

The fluid in the chamber may be a gas, such as air, or may be a fluid or gel. The fluid is selected to expand when subjected to heat to force the diaphragm to displace from a first position to a second position, such as from the position inFIG. 4Bto the position shown inFIG. 4A. For example, as the temperature of the fluid in the heating chamber580expands, the volume of the flow passage590decreases. This forces fluid in the flow passage590to exit the flow passage590though the one-way check valve592toward the drainage site320. As the temperature of the heating element584decreases, the temperature of the fluid in the heating chamber580decreases, and the volume correspondingly decreases. This causes the diaphragm588to move from its position in the flow passage590, as is shown inFIG. 4Atoward the heating chamber580, increasing the volume of the flow passage as is shown inFIG. 4B. Accordingly, fluid may be drawn though the one way check valve594from the inlet tube325.

The heating element may be a resistive heating element that converts electrical current to heat, and may be operated to gradually increase the volume of the pump chamber429as the fluid expands or to rapidly increase the volume of the pump chamber429. When operated to slowly heat the fluid in the heating chamber, fluid flow from the flow passage can be gradual. When operated to rapidly increase the volume of the flow passage, fluid flow from the flow passage can be relatively rapid. This rapid movement of fluid can serve to clear blockages in the tubes or the drainage location. When the drainage site is a bleb, the rate at which fluid is expelled to the bleb can be controlled to maintain the bleb at a desirable size and/or pressure. In other words, by controlling fluid flow rates to the drainage site, the drainage site can be maintained in an optimal fashion.

In some embodiments, the heating element is simply turned off or not powered to permit the fluid to cool and gradually decrease in volume in order to reduce the volume of the heating chamber580. When the heating element operates to gradually decrease the volume of the heating chamber580, fluid flow from the inlet tube325into the flow passage590can be gradual. Both the speed of the deflection and the overall cycle frequency can be important in driving the flow.

In some embodiments, activation of the flow system370is based on the flow controller315comprising one or more electronic pressure sensors that may be located in pressure areas P1, P2, and/or P3(shown inFIG. 2). If IOP is high, the flow controller315may determine that pumping action is desired in order to lower the IOP. To do this, electrical current is passed through the resistive heating element584to change the temperature of the fluid in the heating chamber580. This in turn increases the volume of fluid in the heating chamber580. To accommodate the increase in volume, the flexible diaphragm588expands into the flow passage590, displacing the drainage fluid to force fluid out of the exit port574. The current may then be stopped and the heating element may be allowed to cool to an ambient temperature, causing the flexible diaphragm to return to its original position. The cycle may then be repeated if additional pumping is determined to be desired. Accordingly, the pump514may be cycled or actuated a plurality of times to force the drainage fluid past the pump into the drainage site.

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.