Patent Application
20120123315
The present invention generally relates to different types of intraocular shunts.
Glaucoma is a disease of the eye that affects millions of people. Glaucoma is associated with an increase in intraocular pressure resulting either from a failure of a drainage system of an eye to adequately remove aqueous humor from an anterior chamber of the eye or overproduction of aqueous humor by a ciliary body in the eye. Build-up of aqueous humor and resulting intraocular pressure may result in irreversible damage to the optic nerve and the retina, which may lead to irreversible retinal damage and blindness.
Glaucoma may be treated in a number of different ways. One manner of treatment involves delivery of drugs such as beta-blockers or prostaglandins to the eye to either reduce production of aqueous humor or increase flow of aqueous humor from an anterior chamber of the eye. Glaucoma may also be treated by surgical intervention that involves placing a shunt in the eye to result in production of fluid flow pathways between an anterior chamber of an eye and various structures of the eye involved in aqueous humor drainage (e.g., Schlemm's canal, the sclera, or the subconjunctival space). Such fluid flow pathways allow for aqueous humor to exit the anterior chamber.
One problem with implantable shunts is that they are composed of a rigid material, e.g., stainless steel, that does not allow the shunt to react to movement of tissue surrounding the eye. Consequently, existing shunts have a tendency to move after implantation, affecting ability of the shunt to conduct fluid away from the anterior chamber of the eye. To prevent movement of the shunt after implantation, certain shunts are held in place in the eye by an anchor that extends for a body of the shunt and interacts with the surrounding tissue. Such anchors result in irritation and inflammation of the surrounding tissue.
Another problem with implantable shunts is that they may become clogged, preventing aqueous humor from exiting the anterior chamber, and resulting in re-occurrence of fluid build-up in the eye. Such a problem may only be fixed by surgical intervention.
Additionally, existing implantable shunts do not effectively regulate fluid flow from the anterior chamber, i.e., fluid flow is passive from the anterior chamber to a drainage structure of the eye and is not regulated by the shunt. If fluid flows from the anterior chamber at a rate greater than it can be produced in the anterior chamber, the chamber will collapse, resulting in significant damage to the eye and requiring surgical intervention to repair. If fluid flow from the eye is not great enough, pressure in the anterior chamber will not be relieved, and damage to the optic nerve and the retina may still occur.
The invention generally provides improved shunts that facilitate drainage of fluid from an organ. Particularly, shunts of the invention address and solve the above described problems with intraocular shunts.
In certain aspects, the invention generally provides shunts composed of a material that has an elasticity modulus that is compatible with an elasticity modulus of tissue surrounding the shunt. In this manner, shunts of the invention are flexibility matched with the surrounding tissue, and thus will remain in place after implantation without the need for any type of anchor that interacts with the surrounding tissue. Consequently, shunts of the invention will maintain fluid flow away for an anterior chamber of the eye after implantation without causing irritation or inflammation to the tissue surrounding the eye.
Although discussed in the context of the eye, the elasticity modulus of the shunt may be matched to the elasticity modulus of any tissue. Thus, shunts of the invention may be used to drain fluid from any organ. In particular embodiments, the organ is an eye. Shunts of the invention may define a flow path from an area of high pressure in the eye (e.g., an anterior chamber) to an area of lower pressure in the eye (e.g., intra-Tenon's space, the subconjunctival space, the episcleral vein, the suprachoroidal space, and Schlemm's canal).
In other aspects, the invention generally provides shunts in which a portion of the shunt is composed of a flexible material that is reactive to pressure, i.e., an inner diameter of the shunt fluctuates depending upon the pressures exerted on that portion of the shunt. Thus, the flexible portion of the shunt acts as a valve that regulates fluid flow through the shunt. After implantation, intraocular shunts have pressure exerted upon them by tissues surrounding the shunt (e.g., scleral tissue) and pressure exerted upon them by aqueous humor flowing through the shunt. When the pressure exerted on the flexible portion of the shunt by the surrounding tissue is greater than the pressure exerted on the flexible portion of the shunt by the fluid flowing through the shunt, the flexible portion decreases in diameter, restricting flow through the shunt. The restricted flow results in aqueous humor leaving the anterior chamber at a reduced rate.
When the pressure exerted on the flexible portion of the shunt by the fluid flowing through the shunt is greater than the pressure exerted on the flexible portion of the shunt by the surrounding tissue, the flexible portion increases in diameter, increasing flow through the shunt. The increased flow results in aqueous humor leaving the anterior chamber at an increased rate.
The flexible portion of the shunt may be any portion of the shunt. In certain embodiments, the flexible portion is a distal portion of the shunt. In certain embodiments, the entire shunt is composed of the flexible material.
Other aspects of the invention generally provide multi-port shunts. Such shunts reduce probability of the shunt clogging after implantation because fluid can enter or exit the shunt even if one or more ports of the shunt become clogged with particulate. In certain embodiments, the shunt includes a hollow body defining a flow path and more than two ports, in which the body is configured such that a proximal portion receives fluid from the anterior chamber of an eye and a distal portion directs the fluid to a location of lower pressure with respect to the anterior chamber.
The shunt may have many different configurations. In certain embodiments, the proximal portion of the shunt (i.e., the portion disposed within the anterior chamber of the eye) includes more than one port and the distal portion of the shunt (i.e., the portion that is located in an area of lower pressure with respect to the anterior chamber such as intra-Tenon's space, the subconjunctival space, the episcleral vein, the suprachoroidal space, or Schlemm's canal) includes a single port. In other embodiments, the proximal portion includes a single port and the distal portion includes more than one port. In still other embodiments, the proximal and the distal portions include more than one port.
The ports may be positioned in various different orientations and along various different portions of the shunt. In certain embodiments, at least one of the ports is oriented at an angle to the length of the body. In certain embodiments, at least one of the ports is oriented 90° to the length of the body.
The ports may have the same or different inner diameters. In certain embodiments, at least one of the ports has an inner diameter that is different from the inner diameters of the other ports.
Other aspects of the invention generally provide shunts with overflow ports. Those shunts are configured such that the overflow port remains closed until there is a pressure build-up within the shunt sufficient to force open the overflow port. Such pressure build-up typically results from particulate partially or fully clogging an entry or an exit port of the shunt. Such shunts reduce probability of the shunt clogging after implantation because fluid can enter or exit the shunt by the overflow port even in one port of the shunt becomes clogged with particulate.
In certain embodiments, the shunt includes a hollow body defining an inlet configured to receive fluid from an anterior chamber of the eye and an outlet configured to direct the fluid to a location of lower pressure with respect to the anterior chamber, the body further including at least one slit. The slit may be located at any place along the body of the shunt. In certain embodiments, the slit is located in proximity to the inlet. In other embodiments, the slit is located in proximity to the outlet. In certain embodiments, there is a slit in proximity to both the inlet and the outlet of the shunt.
In certain embodiments, the slit has a width that is substantially the same or less than an inner diameter of the inlet. In other embodiments, the slit has a width that is substantially the same or less than an inner diameter of the outlet. Generally, the slit does not direct the fluid unless the outlet is obstructed. However, the shunt may be configured such that the slit does direct at least some of the fluid even if the inlet or outlet is not obstructed.
In other aspects, the invention generally provides a shunt having a variable inner diameter. In particular embodiments, the diameter increases from inlet to outlet of the shunt. By having a variable inner diameter that increases from inlet to outlet, a pressure gradient is produced and particulate that may otherwise clog the inlet of the shunt is forced through the inlet due to the pressure gradient. Further, the particulate will flow out of the shunt because the diameter only increases after the inlet.
In certain embodiments, the shunt includes a hollow body defining a flow path and having an inlet configured to receive fluid from an anterior chamber of an eye and an outlet configured to direct the fluid to a location of lower pressure with respect to the anterior chamber, in which the body further includes a variable inner diameter that increases along the length of the body from the inlet to the outlet. In certain embodiments, the inner diameter continuously increases along the length of the body. In other embodiments, the inner diameter remains constant along portions of the length of the body. Exemplary locations of lower pressure include the intra-Tenon's space, the subconjunctival space, the episcleral vein, the subarachnoid space, and Schlemm's canal.
In certain embodiments, shunts of the invention may be coated or impregnated with at least one pharmaceutical and/or biological agent or a combination thereof. The pharmaceutical and/or biological agent may coat or impregnate an entire exterior of the shunt, an entire interior of the shunt, or both. Alternatively, the pharmaceutical and/or biological agent may coat and/or impregnate a portion of an exterior of the shunt, a portion of an interior of the shunt, or both. Methods of coating and/or impregnating an intraocular shunt with a pharmaceutical and/or biological agent are known in the art. See for example, Darouiche (U.S. Pat. Nos. 7,790,183; 6,719,991; 6,558,686; 6,162,487; 5,902,283; 5,853,745; and 5,624,704) and Yu et al. (U.S. patent application serial number 2008/0108933). The content of each of these references is incorporated by reference herein its entirety.
In certain embodiments, the exterior portion of the shunt that resides in the anterior chamber after implantation (e.g., about 1 mm of the proximal end of the shunt) is coated and/or impregnated with the pharmaceutical or biological agent. In other embodiments, the exterior of the shunt that resides in the scleral tissue after implantation of the shunt is coated and/or impregnated with the pharmaceutical or biological agent. In other embodiments, the exterior portion of the shunt that resides in the area of lower pressure (e.g., the intra-Tenon's space or the subconjunctival space) after implantation is coated and/or impregnated with the pharmaceutical or biological agent. In embodiments in which the pharmaceutical or biological agent coats and/or impregnates the interior of the shunt, the agent may be flushed through the shunt and into the area of lower pressure (e.g., the intra-Tenon's space or the subconjunctival space).
Any pharmaceutical and/or biological agent or combination thereof may be used with shunts of the invention. The pharmaceutical and/or biological agent may be released over a short period of time (e.g., seconds) or may be released over longer periods of time (e.g., days, weeks, months, or even years). Exemplary agents include anti-mitotic pharmaceuticals such as Mitomycin-C or 5-Fluorouracil, anti-VEGF (such as Lucintes, Macugen, Avastin, VEGF or steroids).
The shunts discussed above and herein are described relative to the eye and, more particularly, in the context of treating glaucoma and solving the above identified problems relating to intraocular shunts. Nonetheless, it will be appreciated that shunts described herein may find application in any treatment of a body organ requiring drainage of a fluid from the organ and are not limited to the eye.
In conditions of glaucoma, the pressure of the aqueous humor in the eye (anterior chamber) increases and this resultant increase of pressure can cause damage to the vascular system at the back of the eye and especially to the optic nerve. The treatment of glaucoma and other diseases that lead to elevated pressure in the anterior chamber involves relieving pressure within the anterior chamber to a normal level.
The invention generally provides improved shunts that facilitate drainage of fluid from an organ, such as the eye. Particularly, shunts of the invention address and solve problems associated with prior art intraocular shunts.
In certain aspects, the invention generally provides shunts composed of a material that has an elasticity modulus that is compatible with an elasticity modulus of tissue surrounding the shunt. In this manner, shunts of the invention are flexibility matched with the surrounding tissue, and thus will remain in place after implantation without the need for any type of anchor that interacts with the surrounding tissue. Consequently, shunts of the invention will maintain fluid flow away for an anterior chamber of the eye after implantation without causing irritation or inflammation to the tissue surrounding the eye.
Elastic modulus, or modulus of elasticity, is a mathematical description of an object or substance's tendency to be deformed elastically when a force is applied to it. The elastic modulus of an object is defined as the slope of its stress-strain curve in the elastic deformation region:
where lambda (λ) is the elastic modulus; stress is the force causing the deformation divided by the area to which the force is applied; and strain is the ratio of the change caused by the stress to the original state of the object. The elasticity modulus may also be known as Young's modulus (E), which describes tensile elasticity, or the tendency of an object to deform along an axis when opposing forces are applied along that axis. Young's modulus is defined as the ratio of tensile stress to tensile strain. For further description regarding elasticity modulus and Young's modulus, see for example Gere (Mechanics of Materials, 6th Edition, 2004, Thomson), the content of which is incorporated by reference herein in its entirety.
The elasticity modulus of any tissue can be determined by one of skill in the art. See for example Samani et al. (Phys. Med. Biol. 48:2183, 2003); Erkamp et al. (Measuring The Elastic Modulus Of Small Tissue Samples, Biomedical Engineering Department and Electrical Engineering and Computer Science Department University of Michigan Ann Arbor, Mich. 48109-2125; and Institute of Mathematical Problems in Biology Russian Academy of Sciences, Pushchino, Moscow Region 142292 Russia); Chen et al. (IEEE Trans. Ultrason. Ferroelec. Freq. Control 43:191-194, 1996); Hall, (In 1996 Ultrasonics Symposium Proc., pp. 1193-1196, IEEE Cat. No. 96CH35993, IEEE, New York, 1996); and Parker (Ultrasound Med. Biol. 16:241-246, 1990), each of which provides methods of determining the elasticity modulus of body tissues. The content of each of these is incorporated by reference herein in its entirety.
The elasticity modulus of tissues of different organs is known in the art. For example, Pierscionek et al. (Br J Ophthalmol, 91:801-803, 2007) and Friberg (Experimental Eye Research, 473:429-436, 1988) show the elasticity modulus of the cornea and the sclera of the eye. The content of each of these references is incorporated by reference herein in its entirety. Chen, Hall, and Parker show the elasticity modulus of different muscles and the liver. Erkamp shows the elasticity modulus of the kidney.
Shunts of the invention are composed of a material that is compatible with an elasticity modulus of tissue surrounding the shunt. In certain embodiments, the material has an elasticity modulus that is substantially identical to the elasticity modulus of the tissue surrounding the shunt. In other embodiments, the material has an elasticity modulus that is greater than the elasticity modulus of the tissue surrounding the shunt. Exemplary materials includes biocompatible polymers, such as polycarbonate, polyethylene, polyethylene terephthalate, polyimide, polystyrene, polypropylene, poly(styrene-b-isobutylene-b-styrene), or silicone rubber.
In particular embodiments, shunts of the invention are composed of a material that has an elasticity modulus that is compatible with the elasticity modulus of tissue in the eye, particularly scleral tissue. In certain embodiments, compatible materials are those materials that are softer than scleral tissue or marginally harder than scleral tissue, yet soft enough to prohibit shunt migration. The elasticity modulus for anterior scleral tissue is approximately 2.9±1.4×106 N/m2, and 1.8±1.1×106 N/m2 for posterior scleral tissue. See Friberg (Experimental Eye Research, 473:429-436, 1988). An exemplary material is cross linked gelatin derived from Bovine or Porcine Collagen.
The invention encompasses shunts of different shapes and different dimensions, and the shunts of the invention may be any shape or any dimension that may be accommodated by the eye. In certain embodiments, the intraocular shunt is of a cylindrical shape and has an outside cylindrical wall and a hollow interior. The shunt may have an inside diameter from approximately 10 μm to approximately 250 μm, an outside diameter from approximately 190 μm to approximately 300 μm, and a length from approximately 0.5 mm to approximately 20 mm.
In other aspects, the invention generally provides shunts in which a portion of the shunt is composed of a flexible material that is reactive to pressure, i.e., the diameter of the flexible portion of the shunt fluctuates depending upon the pressures exerted on that portion of the shunt.
The flexible portion 15 of the shunt 14 acts as a valve that regulates fluid flow through the shunt. The human eye produces aqueous humor at a rate of about 2 μl/min for approximately 3 ml/day. The entire aqueous volume is about 0.25 ml. When the pressure in the anterior chamber falls after surgery to about 7-8 mmHg, it is assumed the majority of the aqueous humor is exiting the eye through the implant since venous backpressure prevents any significant outflow through normal drainage structures (e.g., the trabecular meshwork).
After implantation, intraocular shunts have pressure exerted upon them by tissues surrounding the shunt (e.g., scleral tissue such as the sclera channel and the sclera exit) and pressure exerted upon them by aqueous humor flowing through the shunt. The flow through the shunt, and thus the pressure exerted by the fluid on the shunt, is calculated by the equation:
where Φ is the volumetric flow rate; V is a volume of the liquid poured (cubic meters); t is the time (seconds); v is mean fluid velocity along the length of the tube (meters/second); x is a distance in direction of flow (meters); R is the internal radius of the tube (meters); ΔP is the pressure difference between the two ends (pascals); η is the dynamic fluid viscosity (pascal-second (Pa·s)); and L is the total length of the tube in the x direction (meters).
When the pressure exerted on the flexible portion 20 of the shunt 16 by sclera 21 (vertical arrows) is greater than the pressure exerted on the flexible portion 20 of the shunt 16 by the fluid flowing through the shunt (horizontal arrow), the flexible portion 20 decreases in diameter, restricting flow through the shunt 16 (
When the pressure exerted on the flexible portion 20 of the shunt 16 by the fluid flowing through the shunt (horizontal arrow) is greater than the pressure exerted on the flexible portion 20 of the shunt 16 by the sclera 21 (vertical arrows), the flexible portion 20 increases in diameter, increasing flow through the shunt 16 (
The invention encompasses shunts of different shapes and different dimensions, and the shunts of the invention may be any shape or any dimension that may be accommodated by the eye. In certain embodiments, the intraocular shunt is of a cylindrical shape and has an outside cylindrical wall and a hollow interior. The shunt may have an inside diameter from approximately 10 μm to approximately 250 μm, an outside diameter from approximately 190 μm to approximately 300 μm, and a length from approximately 0.5 mm to approximately 20 mm.
In a particular embodiments, the shunt has a length of about 6 mm and an inner diameter of about 64 μm. With these dimensions, the pressure difference between the proximal end of the shunt that resides in the anterior chamber and the distal end of the shunt that resides outside the anterior chamber is about 4.3 mmHg. Such dimensions thus allow the implant to act as a controlled valve and protect the integrity of the anterior chamber.
It will be appreciated that different dimensioned implants may be used. For example, shunts that range in length from about 0.5 mm to about 20 mm and have a range in inner diameter from about 10 μm to about 100 μm allow for pressure control from approximately 0.5 mmHg to approximately 20 mmHg.
The material of the flexible portion and the thickness of the wall of the flexible portion will determine how reactive the flexible portion is to the pressures exerted upon it by the surrounding tissue and the fluid flowing through the shunt. Generally, with a certain material, the thicker the flexible portion, the less responsive the portion will be to pressure. In certain embodiments, the flexible portion is a gelatin or other similar material, and the thickness of the gelatin material forming the wall of the flexible portion ranges from about 10 μm thick to about 100 μm thick.
In a certain embodiment, the gelatin used for making the flexible portion is known as gelatin Type B from bovine skin. An exemplary gelatin is PB Leiner gelatin from bovine skin, Type B, 225 Bloom, USP. Another material that may be used in the making of the flexible portion is a gelatin Type A from porcine skin, also available from Sigma Chemical. Such gelatin is available from Sigma Chemical Company of St. Louis, Mo. under Code G-9382. Still other suitable gelatins include bovine bone gelatin, porcine bone gelatin and human-derived gelatins. In addition to gelatins, the flexible portion may be made of hydroxypropyl methycellulose (HPMC), collagen, polylactic acid, polylglycolic acid, hyaluronic acid and glycosaminoglycans.
In certain embodiments, the gelatin is cross-linked. Cross-linking increases the inter- and intramolecular binding of the gelatin substrate. Any method for cross-linking the gelatin may be used. In a particular embodiment, the formed gelatin is treated with a solution of a cross-linking agent such as, but not limited to, glutaraldehyde. Other suitable compounds for cross-linking include 1-ethyl-3-[3-(dimethyamino)propyl]carbodiimide (EDC). Cross-linking by radiation, such as gamma or electron beam (e-beam) may be alternatively employed.
In one embodiment, the gelatin is contacted with a solution of approximately 25% glutaraldehyde for a selected period of time. One suitable form of glutaraldehyde is a grade 1G5882 glutaraldehyde available from Sigma Aldridge Company of Germany, although other glutaraldehyde solutions may also be used. The pH of the glutaraldehyde solution should be in the range of 7 to 7.8 and, more particularly, 7.35-7.44 and typically approximately 7.4+/−0.01. If necessary, the pH may be adjusted by adding a suitable amount of a base such as sodium hydroxide as needed.
Methods for forming the flexible portion of the shunt are shown for example in Yu et al. (U.S. patent application number 2008/0108933), the content of which is incorporated by reference herein in its entirety. In an exemplary protocol, the flexible portion may be made by dipping a core or substrate such as a wire of a suitable diameter in a solution of gelatin. The gelatin solution is typically prepared by dissolving a gelatin powder in de-ionized water or sterile water for injection and placing the dissolved gelatin in a water bath at a temperature of approximately 55° C. with thorough mixing to ensure complete dissolution of the gelatin. In one embodiment, the ratio of solid gelatin to water is approximately 10% to 50% gelatin by weight to 50% to 90% by weight of water. In an embodiment, the gelatin solution includes approximately 40% by weight, gelatin dissolved in water. The resulting gelatin solution should be devoid of air bubbles and has a viscosity that is between approximately 200-500 cp and more particularly between approximately 260 and 410 cp (centipoise).
Once the gelatin solution has been prepared, in accordance with the method described above, supporting structures such as wires having a selected diameter are dipped into the solution to form the flexible portion. Stainless steel wires coated with a biocompatible, lubricious material such as polytetrafluoroethylene (Teflon) are preferred.
Typically, the wires are gently lowered into a container of the gelatin solution and then slowly withdrawn. The rate of movement is selected to control the thickness of the coat. In addition, it is preferred that a the tube be removed at a constant rate in order to provide the desired coating. To ensure that the gelatin is spread evenly over the surface of the wire, in one embodiment, the wires may be rotated in a stream of cool air which helps to set the gelatin solution and affix film onto the wire. Dipping and withdrawing the wire supports may be repeated several times to further ensure even coating of the gelatin. Once the wires have been sufficiently coated with gelatin, the resulting gelatin films on the wire may be dried at room temperature for at least 1 hour, and more preferably, approximately 10 to 24 hours. Apparatus for forming gelatin tubes are described in Yu et al. (U.S. patent application number 2008/0108933).
Once dried, the formed flexible portions may be treated with a cross-linking agent. In one embodiment, the formed flexible portion may be cross-linked by dipping the wire (with film thereon) into the 25% glutaraldehyde solution, at pH of approximately 7.0-7.8 and more preferably approximately 7.35-7.44 at room temperature for at least 4 hours and preferably between approximately 10 to 36 hours, depending on the degree of cross-linking desired. In one embodiment, the formed flexible portion is contacted with a cross-linking agent such as gluteraldehyde for at least approximately 16 hours. Cross-linking can also be accelerated when it is performed a high temperatures. It is believed that the degree of cross-linking is proportional to the bioabsorption time of the channel once implanted. In general, the more cross-linking, the longer the survival of the channel in the body.
The residual glutaraldehyde or other cross-linking agent is removed from the formed flexible portion by soaking the tubes in a volume of sterile water for injection. The water may optionally be replaced at regular intervals, circulated or re-circulated to accelerate diffusion of the unbound glutaraldehyde from the tube. The tubes are washed for a period of a few hours to a period of a few months with the ideal time being 3-14 days. The now cross-linked gelatin tubes may then be dried (cured) at ambient temperature for a selected period of time. It has been observed that a drying period of approximately 48-96 hours and more typically 3 days (i.e., 72 hours) may be preferred for the formation of the cross-linked gelatin tubes.
Where a cross-linking agent is used, it may be desirable to include a quenching agent in the method of making the flexible portion. Quenching agents remove unbound molecules of the cross-linking agent from the formed flexible portion. In certain cases, removing the cross-linking agent may reduce the potential toxicity to a patient if too much of the cross-linking agent is released from the flexible portion. In certain embodiments, the formed flexible portion is contacted with the quenching agent after the cross-linking treatment and, may be included with the washing/rinsing solution. Examples of quenching agents include glycine or sodium borohydride.
The formed flexible portion may be further coated or impregnated with biologics and/or pharmaceuticals. Any pharmaceutical and/or biological agent or combination thereof may be used with shunts of the invention. The pharmaceutical and/or biological agent may be released over a short period of time (e.g., seconds) or may be released over longer periods of time (e.g., days, weeks, months, or even years). In certain embodiments, the pharmaceutical and/or biological agent is selected to regulate the body's response to the implantation of the implant and assist in the subsequent healing process. Exemplary agents include anti-mitotic pharmaceuticals such as Mitomycin-C or 5-Fluorouracil, anti-VEGF (such as Lucintes, Macugen, Avastin, VEGF or steroids).
After the requisite drying period, the formed and cross-linked flexible portion is removed from the underlying supports or wires. In one embodiment, wire tubes may be cut at two ends and the formed gelatin flexible portion slowly removed from the wire support. In another embodiment, wires with gelatin film thereon, may be pushed off using a plunger or tube to remove the formed gelatin flexible portion.
Other aspects of the invention generally provide multi-port shunts. Such shunts reduce probability of the shunt clogging after implantation because fluid can enter or exit the shunt even if one or more ports of the shunt become clogged with particulate. In certain embodiments, the shunt includes a hollow body defining a flow path and more than two ports, in which the body is configured such that a proximal portion receives fluid from the anterior chamber of an eye and a distal portion directs the fluid to a location of lower pressure with respect to the anterior chamber. Exemplary areas of lower pressure include intra-Tenon's space, the subconjunctival space, the episcleral vein, the suprachoroidal space, or Schlemm's canal. Another exemplary area of lower pressure to which fluid may be drained in the subarachnoid space.
The shunt may have many different configurations.
The ports may be positioned in various different orientations and along various different portions of the shunt. In certain embodiments, at least one of the ports is oriented at an angle to the length of the body. In certain embodiments, at least one of the ports is oriented 90° to the length of the body. See for example
The ports may have the same or different inner diameters. In certain embodiments, at least one of the ports has an inner diameter that is different from the inner diameters of the other ports.
The invention encompasses shunts of different shapes and different dimensions, and the shunts of the invention may be any shape or any dimension that may be accommodated by the eye. In certain embodiments, the intraocular shunt is of a cylindrical shape and has an outside cylindrical wall and a hollow interior. The shunt may have an inside diameter from approximately 10 μm to approximately 250 μm, an outside diameter from approximately 190 μm to approximately 300 μm, and a length from approximately 0.5 mm to approximately 20 mm. Shunts of the invention may be made from any biocompatible material. An exemplary material is gelatin. Methods of making shunts composed of gelatin are described above.
Shunts with Overflow Ports
Other aspects of the invention generally provide shunts with overflow ports. Those shunts are configured such that the overflow port remains partially or completely closed until there is a pressure build-up within the shunt sufficient to force open the overflow port. Such pressure build-up typically results from particulate partially or fully clogging an entry or an exit port of the shunt. Such shunts reduce probability of the shunt clogging after implantation because fluid can enter or exit the shunt by the overflow port even in one port of the shunt becomes clogged with particulate.
In certain embodiments, the shunt includes a hollow body defining an inlet configured to receive fluid from an anterior chamber of an eye and an outlet configured to direct the fluid to a location of lower pressure with respect to the anterior chamber, the body further including at least one slit. The slit may be located at any place along the body of the shunt.
While
In certain embodiments, the slit may be at the proximal or the distal end of the shunt, producing a split in the proximal or the distal end of the implant.
In certain embodiments, the slit has a width that is substantially the same or less than an inner diameter of the inlet. In other embodiments, the slit has a width that is substantially the same or less than an inner diameter of the outlet. In certain embodiments, the slit has a length that ranges from about 0.05 mm to about 2 mm, and a width that ranges from about 10 μm to about 200 μm. Generally, the slit does not direct the fluid unless the outlet is obstructed. However, the shunt may be configured such that the slit does direct at least some of the fluid even if the inlet or outlet is not obstructed.
The invention encompasses shunts of different shapes and different dimensions, and the shunts of the invention may be any shape or any dimension that may be accommodated by the eye. In certain embodiments, the intraocular shunt is of a cylindrical shape and has an outside cylindrical wall and a hollow interior. The shunt may have an inside diameter from approximately 10 μm to approximately 250 μm, an outside diameter from approximately 190 μm to approximately 300 μm, and a length from approximately 0.5 mm to approximately 20 mm. Shunts of the invention may be made from any biocompatible material. An exemplary material is gelatin. Methods of making shunts composed of gelatin are described above.
In other aspects, the invention generally provides a shunt having a variable inner diameter. In particular embodiments, the diameter increases from inlet to outlet of the shunt. By having a variable inner diameter that increases from inlet to outlet, a pressure gradient is produced and particulate that may otherwise clog the inlet of the shunt is forced through the inlet due to the pressure gradient. Further, the particulate will flow out of the shunt because the diameter only increases after the inlet.
In exemplary embodiments, the inner diameter may range in size from about 10 μm to about 200 μm, and the inner diameter at the outlet may range in size from about 15 μm to about 300 μm. The invention encompasses shunts of different shapes and different dimensions, and the shunts of the invention may be any shape or any dimension that may be accommodated by the eye. In certain embodiments, the intraocular shunt is of a cylindrical shape and has an outside cylindrical wall and a hollow interior. The shunt may have an inside diameter from approximately 10 μm to approximately 250 μm, an outside diameter from approximately 190 μm to approximately 300 μm, and a length from approximately 0.5 mm to approximately 20 mm. Shunts of the invention may be made from any biocompatible material. An exemplary material is gelatin. Methods of making shunts composed of gelatin are described above.
Any of a variety of methods known in the art may be used to implant the shunts of the invention into an eye. In certain embodiments, shunts of the invention may be implanted using an ab externo approach (entering through the conjunctiva) or an ab interno approach (entering through the cornea).
In certain embodiments, the shunts of the invention are implanted using an ab interno approach. Ab interno approaches for implanting an intraocular shunt are shown for example in Yu et al. (U.S. Pat. No. 6,544,249 and U.S. patent application number 2008/0108933) and Prywes (U.S. Pat. No. 6,007,511), the content of each of which is incorporated by reference herein in its entirety.
Shunts of the invention may be implanted to drain fluid, e.g., aqueous humor, from the anterior chamber of the eye to various drainage structures of the eye. Exemplary drainage structures include Schlemm's canal, the subconjunctival space, the episcleral vein, the suprachoroidal space, or the intra-Tenon's space. In certain embodiments, fluid is drained to the subarachnoid space.
In particular embodiments, shunts of the invention are implanted to create a drainage passageway from the anterior chamber to the intra-Tenon's space.
Numerous techniques may be employed to ensure that after piercing the sclera 205, the hollow shaft 206 does not pierce Tenon's capsule 207. In certain embodiments, the methods of the invention involve the use of a hollow shaft 206, in which a portion of the hollow shaft extends linearly along a longitudinal axis and at least one other portion of the shaft extends off the longitudinal axis. For example, the hollow shaft 206 may have a bend in the distal portion of the shaft, a U-shape, or an arcuate or V-shape in at least a portion of the shaft. Examples of such hollow shafts 206 suitable for use with the methods of the invention include but are not limited to the hollow shafts 206 depicted in Yu et al. (U.S. patent application number 2008/0108933). In embodiments in which the hollow shaft 206 has a bend at a distal portion of the shaft, intra-Tenon's shunt placement can be achieved by using the bent distal portion of the shaft 206 to push Tenon's capsule 207 away from the sclera 205 without penetrating Tenon's capsule 207. In these embodiments, the tip of the distal end of the shaft 206 does not contact Tenon's capsule 207.
In other embodiments, a straight hollow shaft 206 having a beveled tip is employed. The angle of the beveled tip of the hollow shaft is configured such that after piercing the sclera 205, the hollow shaft 206 does not pierce Tenon's capsule 207. In these embodiments, the shaft 206 is inserted into the eye 202 and through the sclera 205 at an angle such that the bevel of the tip is parallel to Tenon's capsule 207, thereby pushing Tenon's capsule 207 away from the sclera 205, rather than penetrating Tenon's capsule 207, and allowing for deployment of a distal portion of the shunt 201 into the intra-Tenon's space 208.
Once a distal portion of the hollow shaft 206 is within the intra-Tenon's space 208, the shunt 201 is then deployed from the shaft 206 of the deployment device 200, producing a conduit between the anterior chamber 204 and the intra-Tenon's space 208 to allow aqueous humor to drain from the anterior chamber 204 (See
As will be appreciated by one skilled in the art, individual features of the invention may be used separately or in any combination. Particularly, it is contemplated that one or more features of the individually described above embodiments may be combined into a single shunt.
References and citations to other documents, such as patents, patent applications, patent publications, journals, books, papers, web contents, have been made throughout this disclosure. All such documents are hereby incorporated herein by reference in their entirety for all purposes.
The invention may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. The foregoing embodiments are therefore to be considered in all respects illustrative rather than limiting on the invention described herein.
