Patent Application
20100119696
The present disclosure generally relates to methods, systems and apparatus for relieving fluid pressure from an organ such as (but not limited to) the eye. More particularly, the present disclosure relates to methods and apparatus for treating glaucoma by relieving the pressure within the eye.
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 the eye's drainage system to adequately remove aqueous humor from the anterior chamber of the eye or the overproduction of aqueous humor by the ciliary body. The build-up of aqueous humor and resulting intraocular pressure can cause irreversible damage to the optic nerve and the retina, which may potentially lead to irreversible retinal damage and blindness.
Presently, glaucoma can be treated in a number of different ways, The most widely practiced treatment of glaucoma involves delivery of drugs such as beta-blockers or prostaglandins to the eye (typically in the form of eye drops) to either reduce the production of aqueous humor or increase the flow of aqueous humor from the anterior chamber of the eye. Glaucoma may also be treated by surgical intervention such as trabeculectomy. Trabeculectomy or similar surgical procedures involve creating conduits between the anterior chamber and the various structures involved in aqueous humor drainage such as Schlemm's canal, the sclera, and the subconjunctival space in order to provide a pathway for the aqueous humor to exit the anterior chamber.
While these methods of treating glaucoma have been generally effective, they are not without their drawbacks. In the case of medicinal treatments of the eye, patient compliance is an issue because such treatments require regular (i.e., daily) intervention. With respect to surgical procedures such as a trabeculectomy, such procedures are very invasive and can cause irreversible changes to the eye. For example, trabeculectomy results in the permanent removal of a segment of the trabecular meshwork, inflammation and scarring in the quadrant of the eye where the surgery was performed, and the formation of a filtering bleb. Implantation of shunts such as the Molteno, Barveldt, or Ahmed shunts induce chronic foreign body reactions and the formation of a chronic subconjunctival bleb. In addition, such surgical treatment of glaucoma often requires long healing times and can result in certain complications such as infection, scarring, hypotony or cataracts.
More recently, less invasive surgical treatments have been developed. These treatments do not require incision into the conjunctiva of the eye. One example of a less invasive surgical procedure is described in U.S. Pat. No. 6,544,249, the entire disclosure of which is hereby incorporated by reference. U.S. Pat. No. 6,544,249 discloses methods and apparatus for introducing a small bioabsorbable and biocompatible drainage canal, referred to therein as a microfistula tube into the portion of the eye that extends from the anterior chamber to the sub-conjunctival space. The procedure described in U.S. Pat. No. 6,544,249 does not require incision of the conjunctiva. Instead, introduction of the bioabsorbable microfistula tube is accomplished by an ab interno approach—through the cornea of the eye to the desired location (between the anterior chamber and the sub-conjunctival space.) U.S. Pat. No. 6,544,249 also generally describes a delivery apparatus for introducing and implanting the bioabsorbable microfistula tube.
U.S. Pat. No. 6,007,511, the entire disclosure of which is incorporated herein by reference, likewise discloses less invasive methods and apparatus for treating glaucoma. As in the above-referenced U.S. Pat. No. 6,544,249, a bioabsorbable drainage tube is introduced into the area between the anterior chamber and the sub-conjunctival space to allow drainage of the aqueous humor from the anterior chamber of the eye. As in U.S. Pat. No. 6,544,249, incision of the conjunctiva is not required.
These new procedures for treating glaucoma offer the promise of a long term cure of glaucoma without the shortcomings of medicinal treatments and without the risks associated with the known and presently practiced surgical procedures described above. Accordingly, it would be desirable to provide improved methods, systems, channels and delivery apparatus for treating glaucoma specifically and for treating other conditions where drainage of accumulated liquid is desired or required.
The present disclosure sets forth improved methods and apparatus for carrying out channel implantation into an organ of the body such as the eye. It will be appreciated that the methods and apparatus described below may also find application in any treatment of a body organ requiring controlled drainage of a fluid from the organ. Nonetheless, the methods and apparatus for performing such treatment will be described relative to the eye and, more particularly, in the context of treating glaucoma.
The present disclosure relates to an implantable, microfistula channel. The channel has a bioabsorbable body defining an interior flow path. The channel body is made of cross-linked bioabsorbable material such as gelatin and has an expandable outer diameter. The flow path has a diameter of between approximately 50 and 250 microns (μm).
The present disclosure also relates to a method of making an implantable channel. The method includes providing a source of a bio-compatible gelatin solution and providing a generally cylindrical solid support. The support has a diameter of approximately 50 to 250 microns. The method includes contacting the outer surface of the support with the gelatin for a period of time sufficient to coat the support outer surface. A hollow gelatin tube is thus formed on the support. The formed hollow gelatin channel may be dried (cured) for a selected period of time and the formed gelatin tube may be subjected to a cross-linking treatment. The formed and cross-linked gelatin tube is removed from the support.
The present disclosure also relates to an implantation apparatus for implanting a channel into an organ of a subject. The apparatus includes a reusuable portion that includes an apparatus housing. The housing has an open distal end, a proximal end and an interior chamber. The apparatus includes an arm subassembly within the housing that includes one or more movable arms adapted to engage a disposable needle assembly. The apparatus further includes one or more drivers coupled to said one or more moveable arms of the arm sub-assembly.
The present disclosure further relates to systems for implanting a channel into an organ of a subject. The system includes a reusable portion adapted to receive a needle assembly and a disposable portion that includes a needle assembly. The needle assembly has a hollow needle terminating in a sharpened tip and a guidewire and a plunger disposed within the needle. The system includes a microprocessor-based controller including pre-programmed instructions for selective movement of at least the guidewire and the plunger.
The present disclosure further relates to methods of implanting a bioabsorbable channel into an organ of a subject. In the methods described herein, an implantation apparatus including a hollow needle having a pointed distal end, a bioabsorbable channel within the needle assembly and a plunger proximally located relative to the channel is provided. The method includes the steps of introducing the pointed tip of the needle end assembly into the organ of a subject, advancing the needle to the desired area of implantation and actuating the plunger to advance the channel to the desired area of implantation. The method further includes removing the needle from the organ.
a)-(f) are schematic views of the implantation apparatus of
a)-(d) depicts a series of steps showing an ipsilateral normal channel insertion and placement using a U-shaped or otherwise arcuate needle;
Methods and apparatus for delivering and implanting bioabsorbable tubes or shunts are generally disclosed in U.S. Pat. Nos. 6,544,249 and 6,007,511, both of which have been previously incorporated by reference in their entireties. As set forth therein, and also with reference to
The methods, systems, apparatus and channels described herein likewise utilize a hollow needle and a bioabsorbable channel delivered by the needle ab interno through the cornea 19 or the surgical limbus 17. As used herein, the term “channel” includes hollow microfistula tubes similar to the type generally described in U.S. Pat. No. 6,544,249 as well as other structures that include one or more flow paths therethrough.
Turning now to a discussion of the methods, systems, apparatus and channels that embody the present invention, as generally shown in
As will be described in greater detail below, channel 26 may be delivered to and implanted within the desired location of the eye in any one of several different ways. The method of implantation (and system) may be fully automated, partially automated (and, thus, partially manual) or completely manual. For example, in a fully automated procedure, channel 26 may be delivered by robotic implantation whereby a surgeon controls the advancement of needle 22, plunger 32, optional guidewire 28 and, as a result, channel 26 by remotely controlling a robot. In such fully automated, remotely controlled procedures, the surgeon's hands typically do not contact implantation apparatus 10 during the surgical procedure.
Alternatively, channel 26 may be delivered to the desired area of the eye with a “handheld” implantation apparatus, embodiments of which are shown in
In the case of fully manual apparatus and methods, which are also discussed below and shown in
One example of an implantation apparatus 10 and system embodying the present invention is shown in
As shown in
Housing 34 and door 36 may be made of any material that is suitable for use in medical devices. For example, housing 34 may be made of a lightweight aluminum or, more preferably, a biocompatible plastic material. Examples of such suitable plastic materials include polycarbonate and other polymeric resins such as Delrin® and Ultem®. Similarly, door 36 may be made of a plastic material such as the above-described materials including polymers and polymer resins such as polycarbonate, Delrin® and Ultem®. In a preferred embodiment, door may be substantially translucent or transparent.
Re-usable portion 30 of implantation apparatus 10 houses the components required to effect movement of the needle assembly 20 components during the implantation procedure. As shown in
With respect to the embodiments of
As indicated above, each of the motors 44, 46 and 48 (or other drivers) is coupled to one of the lead screws 52(a)-(c), which, in turn, are coupled to movable arms 54, 58 and 62 of arm sub-assembly 55. For example, with specific reference to the embodiment of
As shown in the Figures, arms 54, 58 and 62 are preferably of varying axial lengths. Each of the arms 54, 58 and 62 includes a slot for receiving a portion of the needle assembly 20 (described below.) Thus, guidewire arm 54 includes a guidewire hub slot 57; plunger arm 58 includes a plunger hub slot 59 and needle arm 62 includes a needle hub slot 63.
In a preferred embodiment, each of the arms 54, 58 and 62 includes at its distal and/or proximal ends a portion having an enlarged cross-section. The distal “blocks” 54(a), 58(a) and 62(a) provide abutment surfaces which limit axial movement of the respective arms. As will be seen from the discussion of the implantation method, the distal blocks which also define slots 59, 62 and 63 limit movement of the particular arms, thereby ensuring that the guidewire, plunger and channel 26 do not move beyond a pre-determined distance. Similarly, wall 65 of housing 34 limits movement of needle arm 62, likewise ensuring that the needle does not penetrate the eye beyond a desired distance. Proximal blocks 58(a), 58(b) and 58(c) (not shown) likewise provide an abutment surfaces for contacting fixed collars 53 on lead screws 52(a)-(c). Contact between the surfaces of blocks 58(a), 58(b) and 58(c) and respective collars 53 provides an indication that arms of arm subassembly 55 are in their rearmost or “hard stop” position, discussed below. Blocks 58(a)-(c) also include internal threaded nuts through which lead screws 50(a)-(c) travel.
As further seen in
As noted above, arm sub-assembly 55 is adapted to receive needle assembly 20. Needle assembly, shown in
As best shown in
Another embodiment of a handheld implantation apparatus is shown in
As further shown in
Needle assembly 20 is mounted onto reusable handheld portion 30. More particularly, as shown in
Implantation apparatus 10 includes a handle 180. Handle 180 preferably includes groove 206 along the side wall for easy gripping by the surgeon. As shown in
Reusable portion 30 of handheld implantation apparatus 10 generally depicted in
Regardless of the means of control, in the example shown in
Of course, as described in relation to the embodiment of
Turning to
Placement of channel 26 onto guidewire 28 may be achieved by turning thumbwheel 116 in a first direction to retract needle assembly 122 and hollow needle 124, thereby revealing the distal end of guidewire 28 and plunger tube 32. At that point, channel 26 is placed (typically manually) on guidewire 28 so that the proximal end thereof (the end opposite the leading end of channel 26) of channel comes into contact with the distal end of plunger 32. Thumbwheel 116 is then turned in an opposite direction to the first direction to slide needle 124 over plunger tube 32 and channel 26.
Channel 26 is now ready for implantation. During the implantation process, needle 124 is inserted into the eye and, more specifically, the cornea 19 or surgical limbus 17 of the eye in the manner described above and in U.S. Pat. No. 6,544,249. Needle 124 is advanced across anterior chamber 16 and into the sub-conjunctival space 18, stopping short of the conjunctiva 14. Thumbwheel 116 is then rotated again in the first direction to retract needle 124 and thereby expose channel 26. Once in place, guidewire is retracted, releasing microfistula 26 from guidewire 28. Retraction of guidewire may be achieved manually by a simple pulling of guidewire 28 at the proximal end of apparatus 110. Once channel 26 is in its final position, needle 124 is removed.
In contrast to the embodiment of
For placement of channel 26 onto guidewire 28, trigger 156 is pulled, resulting in rearward movement of syringe 154 and needle 22. Rearward movement of needle 22 exposes guidewire 28 and allows for placement of channel 26 onto guidewire. Release of the trigger 158 advances needle 22 to cover guidewire 28 and channel 26. As in the previous embodiments, needle 22 pierces cornea 19 or surgical limbus 17, and is advanced through anterior chamber 16 to the desired location of the eye (i.e. the area between the sub-conjunctival space 18 and the anterior chamber). Trigger 156 is once again pulled to move needle assembly 158 in a rearward direction thereby exposing channel 26 carried by guidewire 28. Once the surgeon has determined that the channel 26 is in the desired location, guidewire 28 is retracted, thereby releasing channel 26. As shown in
Although selective movement of guidewire 28, needle assembly, plunger 32 or guidewire holder 24 with the channel 26 using electrical, mechanical or even some manual means have been described, other means for actuating movement of these components may also be used instead of or in addition to such means. For example, movement of the various component parts may be achieved by pneumatic control or fluidic control.
The method of implanting channel 26 using implantation apparatus will now be described. The method will be described with particular reference to the embodiment of
At the outset, it will be appreciated that the implantation of channel 26 requires precise placement of the channel 26 in the correct location within the eye. Moreover, it will also be appreciated that the distances traveled by the channel 26, plunger 32, guidewire 28 and needle 22 are typically measured in millimeters. Such precision may be difficult for even the most skilled surgeon to achieve by manual manipulation (due to natural hand tremors in humans). Accordingly, in embodiments other than the manual hand-held implanters in
In a first step, preferably performed during factory assembly, channel 26 is loaded into needle assembly 20. During loading, the distal tip of guidewire preferably extends slightly beyond the beveled tip of hollow needle 22. Channel 26 may be manually placed on guidewire 28 until proximal end of channel 26 contacts the distal end of plunger 32. Guidewire 28, with channel 26 placed thereon is then retracted into hollow needle 22.
Prior to loading needle assembly 20 into apparatus 30, pre-positioning of arm-subassembly may be desired or required. Thus, in a first step, all motors are activated to retract guidewire arm 54, plunger arm 58 and needle arm 62 to a proximal most position such that the proximal end surfaces of the arms abut against collars 53. This “hard stop” position is shown schematically in
After the advancement of the plunger and guidewire described above, motor 48 is activated and needle arm 62 is moved in a rearward direction such that needle 22 is withdrawn from its position shown in
From the preceding discussion, it will be appreciated that bioabsorbable microfistula channel is implanted by directing the needle across the anterior chamber, entering the trabecular meshwork (preferably between Schwalbe's Line and the Scleral spur), and directing the needle through the sclera until the distal tip of the needle is visible in the subconjunctival space. The length of the channel through the sclera should be approximately 2-4 mm. Once the surgeon has placed the needle in this location, he may actuate the implanter to begin the release steps. The channel is released and the needle is withdrawn such that approximately 1-2 mm of the channel resides in the sub conjunctival space, approximately 2-4 mm resides in the scleral channel, and approximately 1-2 mm resides in the anterior chamber. Once the channel is released, the surgeon removes apparatus needle 20.
Proper positioning of the bioabsorbable channel 26 should be carefully controlled for at least the following reasons. If the surgical procedure results in the formation of a bleb, the more posterior the bleb is located, the fewer complications can be expected. Additionally, the bleb interferes less with eyelid motion and is generally more comfortable for the patient. Second, a longer scleral channel provides more surface contact between the channel and the tissue providing better anchoring. Third, the location of the channel may play a role in stimulating the formation of active drainage structures such as veins or lymph vessels. Finally, the location of the channel should be such so as to avoid other anatomical structures such as the ciliary body, iris, and cornea. Trauma to these structures could cause bleeding and other complications for the patient. Additionally, if the bleb is shallow in height and diffuse in surface area, it provides better drainage and less mechanical interference with the patient's eye. Tall, anteriorly located blebs are more susceptible to complications such as conjunctival erosions or blebitis which require further intervention by the surgeon.
The ab interno approach provides better placement than the ab externo approach because it provides the surgeon better visibility for entering the eye. If directing the needle from an ab externo approach, it is often very difficult for the surgeon to direct the needle to the trabecular meshwork (between Schwalbe's line and the scleral spur) without damaging the cornea, iris, or ciliary body.
In an alternative method of implantation, it is possible to direct the needle from the trabecular meshwork into the suprachoroidal space (instead of the subconjunctival space) and provide pressure relief by connecting these two spaces. The suprachoroidal space also called supracilliary space has been shown to be at a pressure of a few mmHg below the pressure in the anterior chamber.
Common to all of the embodiments of handheld implantation apparatus are a needle assembly including a hollow needle. In a preferred embodiment, hollow needle 22 may be any needle suitable for use in medical procedures. As such, needle 22 is made of a hard and rigid material such as stainless steel with a beveled sharpened distal tip. Needle 22 is bonded, welded, overmolded, or otherwise attached to the needle mount 23 and/or hub that is adapted for placement onto the distal end of a needle assembly. The needle 22 is disposable and intended for one time use.
Hollow needle 22 and indeed, the entire needle assembly may be sterilized by known sterilization techniques such as autoclaving, ethelyne oxide, plasma, electron beam, or gamma radiation sterilization. In a preferred embodiment, needle 22 is a 25 gauge thin walled needle that is commercially available from Terumo Medical Corp., Elkton, Md. 21921. The inside diameter of hollow needle 22 must be sufficient to accommodate optional guidewire 28, channel 26 and plunger tube 32, with an inner diameter of 200-400 μM being preferred. The usable length of needle 22 may be anywhere between 20-30 mm, although a length of approximately 22 mm is typical and preferred. Preferably, needle 22 may include markings or graduations 27 near the distal tip as shown in
While a straight hollow needle of the type typically used in medial procedures is generally preferred, in an alternative to the needle shown in the
Providing a piercing end 96 that is bent away from the plane of needle shaft 98 can facilitate manipulation and rotation of needle 22 during implantation of tube 26. It may also provide the surgeon with greater flexibility in terms of selecting the corneal entry site and the ultimate final position of channel 26. This is perhaps best seen with reference to
For example,
Although the transpupil implant delivery and/or the ipsilateral tangential delivery, if performed correctly, are acceptable methods of delivering channel 26, they do somewhat limit the location of the corneal entry site due to interference with the nose and eye orbit bones. In that regard, an arcuate needle of the type described above and shown in FIGS. 22(a)-(d) and
A further advantage of the arcuate needle and the delivery implant method associated therewith is that microfistula channel 26 can be delivered without crossing the lens i.e., visual axis, thereby reducing the risk of complications. An arcuate needle design may also allow the surgery to be done in patients with abnormal anatomy or who have previously undergone surgery.
In accordance with delivering a microfistula channel 26 using the U-shaped hollow needle 20 of
In a further embodiment, a hollow needle 22 that is bent (but not necessarily in a U-shape as described above), may be provided. A needle of this type is shown in
Whether the needle is U-shaped or bent at an angle .alpha. shown in
Typically, however, guidewire 28 is preferably a narrow gauge wire made of a suitable rigid material. A preferred material is tungsten or stainless steel, although other non-metallic materials may also be used. In a preferred embodiment, guidewire 28 is solid with an outside diameter of approximately 50-200 (ideally 125) microns. Where guidewire 28 is made of tungsten, it may be coated with a Teflon, polymeric, or other plastic material to reduce friction and assist in movement of channel 26 along guidewire 28 during implantation.
Channels 26 useful in the present invention, are preferably made of a biocompatible and preferably bioabsorbable material. The materials preferably have a selected rigidity, a selected stiffness and a selected ability to swell (during manufacture and/or after implantation) in order to provide for secure implantation of the channel in the desired section of the eye. Selecting a material that is capable of a controlled swelling is also desirable. By controlled swelling, it is meant that the swellable material is such that the outer diameter of the channel expands (increases) without decreasing the inner diameter. The inner diameter may increase or remain substantially the same. The materials and methods for making channels described below provide such controlled swelling. By sufficient biocompatibility, it is meant that the material selected should be one that avoids moderate to severe inflammatory or immune reactions or scarring in the eye. The bioabsorbability is such that the channel is capable of being absorbed by the body after it has been implanted for a period of anywhere between 30 days and 2 years and, more preferably, several months such as 4-7 months.
In one embodiment, the material selected for the channels is preferably a gelatin or other similar material. In a preferred embodiment, the gelatin used for making the channel is known as gelatin Type B from bovine skin. A preferred gelatin is PB Leiner gelatin from bovine skin, Type B, 225 Bloom, USP. Another material that may be used in the making of the channels is a gelatin Type A from porcine skin also available from Sigma Chemical. Such gelatin is available 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, microfistula channel may be made of hydroxypropyl methycellulose (HPMC), collagen, polylactic acid, polylglycolic acid, hyaluronic acid and glycosaminoglycans.
In accordance with the present invention, gelatin channels are preferably cross-linked. Cross-linking increases the inter- and intramolecular binding of the gelatin substrate. Any means for cross-linking the gelatin may be used. In a preferred embodiment, the formed gelatin channels are 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 channels are 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 preferably be in the range of 7 to 7.8 and, more preferably, 7.35-7.44 and typically approximately 7.4.+−0.0.01. If necessary, the pH may be adjusted by adding a suitable amount of a base such as sodium hydroxide as needed.
Channels used in the present invention are generally cylindrically shaped having an outside cylindrical wall and, in one embodiment, a hollow interior. The channels preferably have an inside diameter of approximately 50-250 microns and, more preferably, an inside diameter and us, a flow path diameter of approximately 150 to 230 microns. The outside diameter of the channels may be approximately 190-300 with a minimum wall thickness of 30-70 microns for stiffness.
As shown in
The length of the channel may be any length sufficient to provide a passageway or canal between the anterior chamber and the subconjunctival space. Typically, the length of the channel is between approximately 2 to 8 millimeters with a total length of approximately 6 millimeters, in most cases being preferred. The inner diameter and/or length of tube 26 can be varied in order to regulate the flow rate through channel 26. A preferred flow rate is approximately 1-3 microliters per minute, with a flow rate of approximately 2 microliters being more preferred.
In one embodiment, channels 26 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 preferably is devoid of any air bubbles and has a viscosity that is between approximately 200-500 cp and more preferably 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 gelatin channels. 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 below.
Once dried, the formed microfistula gelatin channels are treated with a cross-linking agent. In one embodiment, the formed microfistula gelatin films 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, formed channel 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 channels 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 channel 26. Quenching agents remove unbound molecules of the cross-linking agent from the formed channel 26. 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 channel 26. Formed channel 26 is preferably contacted with the quenching agent after the cross-linking treatment and, preferably, may be included with the washing/rinsing solution. Examples of quenching agents include glycine or sodium borohydride.
The formed gelatin tubes may be further treated with biologics, pharmaceuticals or other chemicals selected to regulate the body's response to the implantation of channel 26 and the subsequent healing process. Examples of suitable agents include anti-mitolic 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 gelatin tubes are removed from the underlying supports or wires. In one embodiment, wire tubes may be cut at two ends and the formed gelatin tube 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 channel.
In
The gelatin tube may also be formed by preparing the mixture as described above and extruding the gelatin into a tubular shape using standard plastics processing techniques. Preparing channel 26 by extrusion allows for providing channels of different cross sections. For example, as shown in
Channels 26 made in accordance with the methods described above, allow for continuous and controlled drainage of aqueous humor from the anterior chamber of the eye. The preferred drainage flow rate is approximately 2 microliters per minute, although by varying the inner diameter and length of channel 26, the flow rate may be adjusted as needed. One or more channels 26 may be implanted into the eye of the patient to further control the drainage.
In addition to providing a safe and efficient way to relieve intraocular pressure in the eye, it has been observed that implanted channels disclosed herein can also contribute to regulating the flow rate (due to resistance of the lymphatic outflow tract) and stimulate growth of functional drainage structures between the eye and the lymphatic and/or venous systems. These drainage structures evacuate fluid from the subconjunctival which also result in a low diffuse bleb, a small bleb reservoir or no bleb whatsoever.
The formation of drainage pathways formed by and to the lymphatic system and/or veins may have applications beyond the treatment of glaucoma. Thus, the methods of channel implantation may be useful in the treatment of other tissues and organs where drainage may be desired or required.
In addition, it has been observed that as the microfistula channel absorbs, a “natural” microfistula channel or pathway lined with cells is formed. This “natural” channel is stable. The implanted channel stays in place (thereby keeping the opposing sides of the formed channel separated) long enough to allow for a confluent covering of cells to form. Once these cells form, they are stable, thus eliminating the need for a foreign body to be placed in the formed space.
While the methods, apparatus and systems of this disclosure have been described with reference to certain embodiments, it will be apparent to those skilled in the art that numerous modifications and variations can be made within the scope and spirit of the inventions as recited in the appended claims.
This application is a continuation of U.S. application Ser. No. 11/771,805, filed on Jun. 29, 2007, which claims the benefit of and priority to U.S. Provisional Patent Application No. 60/806,402, filed Jun. 30, 2006, both of which are hereby incorporated by reference in their entireties.
| Number | Date | Country | |
|---|---|---|---|
| 60806402 | Jun 2006 | US |
| Number | Date | Country | |
|---|---|---|---|
| Parent | 11771805 | Jun 2007 | US |
| Child | 12620557 | US |
