Abstract:
Sutureless, implantable fluid shunting devices and associated methods for controlling the pressure of fluids within anatomical spaces or cavities of the body. The device generally comprises a tube having a diffusion barrier (e.g., diffusion chamber) formed on a proximal end thereof. Fluid which flows through the tube will collect within the diffusion chamber and will diffuse outwardly therethrough. However, the presence of the diffusion chamber will prevent microbes, cells or other matter from interfering with or backflowing through the tube. Additionally, the tube may be provided with a pressure-openable aperture through which fluid from the tube may flow into the diffusion chamber. Such pressure-openable aperture will remain closed, until the pressure of fluid within the tube exceeds a predetermined maximum pressure P MAX . In this manner, the pressure-openable aperture will limit the amount of fluid drained from the anatomical space or cavity of the body, thereby avoiding hypotony within such anatomical space or cavity. The diffusion barrier of the device is preferably configured to fit between, and to be engaged by, adjacent recti muscles of the eye. Such engagement of the diffusion barrier with the adjacent recti muscles serves to prevent unwanted migration or post-implantation movement of the device, without the need for suturing of the device to the tissue of the eye.

Description:
RELATED APPLICATION  
       [0001]     This application is a continuation-in-part of U.S. patent application Ser. No. 08/738,332 filed Oct. 25, 1996 entitled “Implantable Devices and Methods for Controlling the Flow of Fluids Within the Body.” 
     
    
     FIELD OF THE INVENTION  
       [0002]     The present invention relates generally to medical apparatus and methods, and more particularly to a device which is implantable in a mammalian body to control the pressure of fluid within a body cavity by shunting such fluid to another site within the body, when the fluid pressure within the body cavity reaches a pre-determined level.  
       BACKGROUND OF THE INVENTION  
       [0003]     A number of diseases and disorders in humans and other mammals are characterized by the build-up of excessive fluid pressure within one or more body cavities. In many instances, implantable devices or surgical procedures may be used to shunt excessive fluid from the body cavity wherein the excessive pressure build up is present, to one or more other sites within the body, as a means of receiving the undesirable pressure buildup, and thereby deterring the development of undesirable sequelae which may result from such pressure build-up.  
         [0000]     i. Glaucoma  
         [0004]     Glaucoma is a disease of the eye which is characterized by high intraocular pressure, and is among the leading causes of blindness in the world. In general, glaucoma results from a defect in the functional drainage system, whereby naturally occurring endogenous fluid (e.g., aqueous humor) is drained from the interior of the eye. The result of this decreased functional drainage of the eye is three-fold: a) increased intraocular pressure, b) degeneration of the optic nerve and supporting tissue at the optic nerve head (disk), and c) progressive loss of the visual field.  
         [0005]     Individual cases of glaucoma are generally classified, on the basis of etiology, into two categories. These two major are “closed angle glaucoma” and “open angle glaucoma”.  
         [0006]     In closed angle glaucoma (syn. “angle-closure glaucoma”, “narrow-angle glaucoma”, “pupillary block glaucoma”) excessive fluid accumulates within the anterior chamber of the eye due to the gradual closure of an anterior angle formed by the junction of the iris and the inner surface of the trabecular mesh work through which the aqueous humor is normally reabsorbed. Closure of this anatomical angle prevents normal drainage of aqueous humor from the anterior chamber of the eye.  
         [0007]     In open angle glaucoma (syn. “chronic simple glaucoma” “simple glaucoma”, “wide-angle glaucoma) the angle of the anterior chamber remains normal, but the drainage of aqueous humor from the anterior chamber is impeded or blocked by other means, such as edema or swelling of the trabecular spaces, abnormal pigment dispersion, or non-perforating injury to the eye resulting in vascular congestion.  
         [0008]     Various pharmacologic modes of treatment have been used to lessen the intraocular fluid pressure in glaucoma patients. Drugs which have been administered to treat glaucoma have included parasympathomimetic agents of the choline ester type (e.g., bethanechol, carbachol and methacholine), carbonic anhydrase inhibitors (e.g., acetazolamide), anticholinesterase agents (e.g., physostigmine, pilocarpine, demecarium, echothiophate and isoflurophate), sympathomimetic agents (e.g, epinephrine, phenylephrine) and β-adrenergic blocking agents (e.g., tymolol). However, these various drug therapies for glaucoma are sometimes associated with significant untoward effects, including headache, blurred vision, allergic reactions, retinal detachment, phacodinesis, histological changes within the eye and potential interactions with other drugs.  
         [0009]     As an alternative to pharmacologic modes of therapy, at least some glaucoma patients may be treated surgically by creating surgical openings into the anterior chamber of the eye, to facilitate drainage of excess aqueous humor from the anterior chamber. Many of these surgical techniques involve the formation of an opening or hole into the anterior chamber, under the conjunctiva and/or scleral flap such that fluid will be drained by filtration from the anterior chamber of the eye, into the tissues located within the lateral wall of the eye. The major problems associated with these surgical filtration procedures stem from the size of the opening or hole made into the anterior chamber. These problems include hypotony, synechiae, inflammation, cataract, corneal decompensation (edema), vitritis, choroidal separation (detachment), macular edema, and infections which may cause endophthalmitis. Moreover, such glaucoma filtration surgery is often unsuccessful due to the formation of dense fibrovascular connective tissue (e.g., scar tissue) around the surgical opening formed into the anterior chamber. Such proliferation of connective tissue tends to close off the surgically-formed opening into the anterior chamber, thereby deterring or preventing the desired filtration of aqueous humor into the subconjunctival space.  
         [0010]     In view of post-surgical complications associated with the development of fibrovascular connective tissue (e.g., scar tissue) around the surgical site, a number of implantable drainage devices have been used to ensure that the desired filtration and outflow of aqueous humor through the surgically-formed opening will continue, despite the formations of, scar tissue during the post operative period. Examples of implantable shunts or other implantable apparatus which have previously been implanted into the eye for drainage of aqueous humor from the anterior chamber of the eye include those described in U.S. Pat. Nos. 4,750,901 (Molteno), 5,041,081 (Odrich), 5,476,445 (Baerveldt), 4,886,488 (White), 5,454,796 (Krupin), 5,397,300 (Baerveldt), 5,372,577 (Ungerleider), 5,338,291 (Speckman, et al.), 5,300,020 (L&#39;Esperance), 5,178,604 (Baerveldt, et al.), 5,171,213 (Price), 5,092,837 (Klein et al.), 4,968,296 (Klein et al.), 4,946,436 (Smith), 4,936,825 (Ungerleider), 4,886,488 (White), 4,806,382 (Burns et al.), 4,554,918 (White), 4,521,210 (Wong), 4,428,746 (Mendez), 4,184,491 (McGannon), 4,157,718 (Baehr), 4,030,480 (Meyer), 5,433,701 (Rubinstein), 5,346,464 (Camras), 5,073,163 (Lippman), 4,604,087 (Joseph), 5,180,362 (Worst), 5,520,631 (Li et al.).  
         [0011]     The major disadvantage associated with the use of implantable shunts for treatment of glaucoma is that, in the immediate post operative period, the shunt may facilitate excessive fluid drainage which results in hypotony within the anterior chamber, flattening of the anterior chamber and potential choroidal detachment and/or phthisis bulbi. Such excessive post-operative fluid outflow may also result in expansion of the fibrous capsule located beneath the rectus muscles of the eye. Such expansion of the fibrous capsule can stretch and tighten the rectus muscles, thereby inducing heterotropia and impairing the motility of the eye in the quadrant wherein the implant is located. Additionally, due to the size of some of these shunt devices, the bulky presence of the device itself within the subconjunctival space can cause scleral erosion, changes in the natural curvature of the eye, or damage to adjacent vasculature and tissue. Other problems associated with the use of implantable shunt devices for the treatment of glaucoma involve friction and wear imparted by the implanted shunt device, irritation of the iris endothelium caused by insertion of the shunt device into the anterior chamber, and migration of microbes, cells, proteins or other matter through the lumen of the shunt device and into the anterior chamber of the eye.  
         [0012]     Also, the surgical procedures used to implant the prior art fluid shunting devices have typically been laborious in nature and have typically required that suturing of the fluid shunting device to the surrounding tissue of the host, to hold the fluid shunting device at its desired location within the eye. The installation of sutures to anchor the implanted fluid shunting device is time consuming and, in cases where such sutures are not properly placed, can result in undesirable tugging, traction or stress on the surrounding tissue and/or disconfiguration of the implanted device. Also, the installation of such sutures can result in unintentional, iatrogenic perforation of the anterior or posterior chabber of the eye, with resultant leakage of aqueous or vitreous humor and/or resultant cellular ingrowth and opacification of the aqueous and/or vitreous humor.  
         [0000]     ii. Hydrocephalus  
         [0013]     Another disorder in which the build-up of abnormal fluid pressure is a hallmark is hydrocephalus. In hydrocephalus, excessive amounts of cerebrospinal fluids accumulate within skull, generally resulting in elevated intracranial pressure. The chronic elevation in intracranial pressure caused by such excessive cerebrospinal fluid within the skull typically results in enlargement of the head, prominence of the forehead, brain atrophy, mental deterioration, and convulsions. Hydrocephalus is maybe of congenital origin or may be an acquired disease. In some patients, hydrocephalus is of sudden onset while in others it is slowly progressive.  
         [0014]     In addition to various pharmacologic therapies, the surgical approach to treatment of hydrocephalus often involves the implantation of a shunt which facilitates drainage of excess cerebrospinal fluid from the intracranial space, to other areas of the body wherein it can be tolerated--most often into the peritoneal cavity. In addition to glaucoma and hydrocephalus, numerous other diseases and disorders involve the buildup of excessive fluid within one or more anatomical spaces (i.e., cavities) of the body, and may be effectively treated by shunting of the excessive fluid from the affected body space (i.e., body cavity) to other region(s) of the body. However, in many cases, it is desirable that an implantable shunt device be used, and that such shunt device be valved or pressure-regulated such that only excessive fluid will be removed from the affected body cavity, while allowing the normal amount of such fluid to remain within the affected body cavity, so long as the pressure within the cavity is in the normal range. Thus, it is desirable for the implanted shunt device to include a pressure-sensitive opening or other pressure-actuated valving apparatus which will allow fluid to flow out of the affected body cavity only when the fluid within the body cavity has exceeded a predetermined maximum pressure.  
         [0015]     One complication associated with the use of implantable shunt devices to drain fluid from body cavities is that proteins, cellular matter, or other debris may block the lumen of the shunt tube thereby interfering with the drainage of fluid through the tube. Also, proliferation of tissue or blebs may compress, collapse, or block the shunt tube. Moreover, pathogenic microorganism or irritating proteins or other matter may migrate through the lumen of the shunt tube into the affected body cavity in a manner which can lead to iatrogenic infection, irritation or inflammation of the affected body cavity.  
         [0016]     Given the above-summarized limitations and drawbacks associated with the implantable fluid-shunting devices of the prior art, it is apparent that no single fluid-shunting device has proven to be optimal for all applications. Accordingly, there exists a need in the art for the development for new implantable fluid-shunting devices which include: a) means for valving or pressure-regulation of the fluid outflow, b) means for preventing microbes, proteins, cells or other matter from clogging the shunt or migrating through the shunt in to the affected body cavity and/or c) means for anchoring the fluid-shunting device in its desired implanted position, without the need for suturing of the device to the adjacent tissue.  
       SUMMARY OF THE INVENTION  
       [0017]     The present invention provides implantable devices for shunting or draining fluid from one intracorporeal location to another. In general, the implantable devices of the present invention comprise an elongate tube having a lumen extending longitudinally therethrough and a diffusion chamber mounted on the proximal end of the tube. The distal end of the tube is open, while the proximal end of the tube is closed. A pressure-openable aperture is formed in a proximal portion of the tube which extends into the interior of the diffusion chamber. Such pressure-openable aperture will open when the pressure of fluid within the lumen of the tube exceeds a predetermined maximum pressure. In this manner, fluid will be permitted to flow from the distal end of the tube, through the lumen of the tube, through the pressure-openable aperture and into the interior of the diffusion chamber. Thereafter, such fluid may diffuse outwardly through the diffusion chamber and into the surrounding tissues or spaces of the body. The diffusion chamber is preferably formed of material which will prevent unwanted matter (e.g., proteins, solid particles greater than a predetermined size, or host cellular matter, such as tissues or individual cells), from entering the interior of the diffusion chamber and (a) interfering with the desired opening and closing of the pressure-openable aperture or (b) migrating through the lumen of the tube and into the region of the body adjacent the distal end of the tube.  
         [0018]     In accordance with the invention, there are provided implantable devices which may be utilized for numerous fluid-shunting applications, including a) the treatment of glaucoma wherein aqueous humor is shunted from the anterior chamber of the eye and b) the treatment of hydrocephalus wherein cerebrospinal fluid is shunted from the intracranial space, into another body cavity (e.g., the peritoneal cavity).  
         [0019]     Further in accordance with the invention, there are provided fluid shunting devices which are implantable in the eye of a mammalian patient, within a subconjunctival pocket formed between two rectus muscles which are anatomically attached to the eye at spaced-apart locations, to control the pressure of fluid within the anterior chamber of the eye without the use of sutures to hold the device in its desired implanted position. A sutureless implantable device in accordance with this aspect of the invention may comprise a) a tube which has a proximal end, a distal end, a side wall, and a lumen extending longitudinally therethrough, b) a diffusion chamber which has an inner cavity formed therewithin. The diffusion chamber of the device is mounted on the proximal end of the tube, such that fluid which enters the distal end of the tube may flow through the lumen of the tube and into the inner cavity of the diffusion chamber. The distal end of the tube is insertable into the anterior chamber of the eye while the diffusion chamber remains positioned within a subconjunctival pocket, posterior to the limbus. The diffusion chamber has a posterior portion which is wider than the distance between the locations at which the adjacent rectus muscled are attached to the eye, and an inter-muscular portion which is slightly narrower than the distance between the rectus muscle attachment points. Preferably, the diffusion chamber also has an anterior portion which like its posterior portion, is wider than the distance between the adjacent rectus muscle attachment points. Such preferred sizing and configuration of the diffusion chamber allows it to be implanted within the subconvunctival pocket with its inter-muscular portion between the rectus muscle attachment points, its anterior portion extending anterior to the rectus muscle attachment points, and its posterior portion extending posterior to the rectus muscle attachment points. When so implanted, the diffusion chamber will remain in substantially fixed position and will be prevented by its engagement with the adjacent rectus muscles from undergoing substantial migration or movement in the longitudinal or lateral directions, without the need for sutures to anchor the diffusion chamber in place. Also, the diffusion chamber may be formed in a generally concave configuration which is analogous to the contour of the ocular bulb, thereby allowing the device to fit easily upon the scleral floor of the subconjunctival pocket, with minimal outward protrusion or tenting of the conjunctival tissue, and minimal discomfort to the patient.  
         [0020]     Further objects and advantages of the present invention will become apparent to those skilled in the art upon reading and understanding the following detailed description and the accompanying drawings.  
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0021]      FIG. 1  is a perspective view of one embodiment of an implantable fluid-shunting device of the present invention.  
         [0022]      FIG. 2  is a longitudinal sectional view through line  2 - 2  of  FIG. 1 .  
         [0023]      FIG. 3  is an enlarged longitudinal sectional view of the proximal-most portion of the fluid-carrying tube component of the device of  FIG. 1 .  
         [0024]      FIG. 4  is a cross-sectional view through line  4 - 4  of  FIG. 1 .  
         [0025]      FIG. 5  is partial transverse sectional view through a portion of a human eye showing an implantable fluid shunting device of the present invention positioned therewithin to relieve excessive pressure within the anterior chamber of the eye.  
         [0026]      FIG. 6  is a schematic showing of a human body wherein an implantable fluid-shunting device of the present invention has been surgically installed to drain excessive cerebrospinal fluid from the brain to the peritoneal cavity.  
         [0027]      FIGS. 7   a - 7   g  are partial perspective views of alternative embodiments of the implantable fluid-shunting device of the present invention.  
         [0028]      FIG. 8  is a perspective view of a sutureless implantable fluid shunting device of the present invention useable to control intraoccular pressure in glaucoma patients.  
         [0029]      FIG. 9  is a longitudinal sectional view trough line  9 - 9  of  FIG. 8 .  
         [0030]      FIG. 10  is a schematic showing of a human eye having the device of  FIG. 10  implanted therein using a sutureless implantation technique of the present invention.  
         [0031]      FIG. 11  is a top plan view of view of the preferred diffusion chamber configuration for the device shown in  FIGS. 8-10 .  
         [0032]      FIG. 12  is a top plan view of an alternative diffusion chamber configuration for the device shown in  FIGS. 8-10 .  
         [0033]      FIG. 13  is a flow diagram for a sutureless method for implanting a fluid shunting device of the type shown in  FIG. 9 .  
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0034]     The following detailed description, and the accompanying drawings to which it refers are provided for purposes of exemplifying and illustrating representative examples and embodiments of the invention only, and are not intended to limit the scope of the invention in any way. Indeed, no effort has been made to exhaustively illustrate and describe all possible embodiments and configurations in which the present invention may take physical form.  
         [0000]     i. Construction and Configuration of the Fluid Shunting Device  
         [0035]     With reference to  FIGS. 1-4 , there is shown a first embodiment of an implantable fluid shunting device  10  comprising an elongate tube  12  having a lumen  14  extending longitudinally therethrough and a diffusion chamber  20  mounted on the proximal end thereof. The tube  12  has an open distal end  16 , a closed proximal end  18  and a pressure openable aperture  30  which is located in a proximal portion PP of the tube  12  which extends into the interior of the diffusion chamber  20 .  
         [0036]     In this regard, the diffusion chamber  20  is mounted on the tube  12  such that the proximal portion PP of the tube  12  adjacent the proximal end  18  thereof, extends into the inner cavity  26  of the diffusion chamber  20 . The diffusion chamber  20  is mounted in sealing contact upon the outer surface of the tube  12  such that fluid which flows out of the tube  12  into the inner cavity  26  of the diffusion chamber  20  will not freely leak therefrom. The diffusion chamber  20  is preferably formed of membranous material (e.g., permeable or semipermeable membrane material) which will permit the fluid which is desired to be drained by the tube  12  to flow from the inner cavity  26  of the diffusion chamber, outwardly and into the region of the body wherein the diffusion chamber  20  is positioned, while preventing predetermined types of unwanted matter (e.g., proteins, solid particles which are greater than a predetermined size, etc.) from passing inwardly through such membrane and into the inner cavity  26  of the diffusion chamber  20 . Additionally, the material of the diffusion chamber  20  will prevent host cellular matter (e.g., tissues or cells such as fibroblasts, endothelium, epithelium, blood cells) from invading (e.g., ingrowing or migrating) the outer surface or inner lumen of the tube  12  and/or the inner cavity  26  of the diffusion chamber  20 .  
         [0037]     In the particular embodiment shown in  FIGS. 1-3 , diffusion chamber  20  is constructed of an upper membrane wall  22   a  and lower membrane wall  22   b.  The upper and lower membrane walls  22   a,    22   b  are sealed to one another at their edges to form a sealed perimeter flange  24 . Such sealing of the upper and lower membrane walls  22   a,    22   b  also forms a fluid-tight seal with the tube  12 , while allowing the proximal portion PP of the tube  12  to extend into the inner cavity  26  of the diffusion chamber  22 .  
         [0038]     In the embodiment shown in  FIGS. 1-3 , suture passage apertures  36  are formed in the diffusion chamber  20  to facilitate suturing of the device  10  at it&#39;s desired position within the body. Also, tissue ingrowth apertures  34  are formed in the diffusion chamber such that tissue may grow through such apertures  34 , thereby firmly anchoring the diffusion chamber  20  in a substantially fixed position within the surgically-created pocket in which it is implanted.  
         [0039]     Also in the embodiment of  FIGS. 1-3 , an optional suture tab  38  having suture passing apertures  40  is affixed to the outer surface of the tube  12 , at a spaced distance proximal to the distal end  16  of the tube  12  to further facilitate suturing of the tube  12  in a desired position within the body.  
         [0040]     Also in the embodiment of  FIGS. 1-3 , an optional concave abutment flange  42  is formed on the outer surface of the tube  12  to facilitate and maintain proper positioning of the tube  12  when implanted within the body in the glaucoma-treatment application described in detail herebelow. It will be appreciated that, although the embodiment shown uses a concave abutment flange  42 , such abutment flange  42  may be of numerous different configurations to facilitate and maintain the desired positioning of the tube  12  in various other anatomical structures and locations of the body.  
         [0041]     The particular details and sizing of this concave abutment flange  42  in connection with a particular application of the invention for the treatment of glaucoma is described in more detail herebelow, and shown in  FIGS. 5 . In many glaucoma treatment applications, it will be desirable for such concave abutment flange  42  to have a width W of approximately 3 mm, a depth D of approximately 1 mm, and a height H of approximately 1 mm.  
         [0042]     The pressure-openable aperture  30  may specifically comprise a slit aperture  30  as shown in the drawings. Such slit aperture  30  is formed in the wall of the proximal portion PP of the tube  12 , to facilitate outflow of fluid from the lumen  14  of the tube  12  into the inner chamber  26  of diffusion chamber  20 . This pressure-openable slit aperture  30  is biased to a closed configuration whereby the opposite sides of the slit aperture  30  are in sealing contact with one another to prevent fluid from flowing from the lumen  14  of the tube  12  into the inner cavity  26  of the diffusion chamber  20  so long as the fluid pressure within the lumen  14  of the tube  12  is below a predetermined maximum pressure P MAX . However, the pressure-openable slit aperture  30  is configured and constructed so as to spread apart (i.e., open) when the fluid pressure within the lumen  14  of the tube  12  exceeds such predetermined maximum pressure P MAX , thereby allowing fluid to flow from the lumen  14  of tube  12  into the inner cavity  26  of the diffusion chamber  20  until the fluid pressure within the lumen  14  of the tube  12  falls below a predetermined aperture closing pressure P CLS , at which time the biasing of the pressure-openable slit aperture  30  will cause such slit aperture  30  to once again assume its closed configuration. The predetermined maximum pressure P MAX  and the predetermined aperture closing pressure P CLS  will be determined on the basis of the intended application of the device  10 , to facilitate drainage of fluid from a body cavity wherein the open distal end  16  of the tube  12  is located, into the diffusion chamber  10  when such pressure exceeds the predetermined maximum pressure P MAX , but to prevent such fluid pressure within the body cavity from falling below the predetermined closing pressure P CLS  so as not to inadvertently drain too much of such fluid from the body cavity. In this manner, the amount of fluid left within the affected body cavity should be sufficient to perform the intended physiological functioning of the fluid (if any), but such fluid will be prevented by the device  10  from over-accumulating within the body cavity in a manner which creates excessive or non-physiological pressure within the body cavity.  
         [0043]     The specific size, shape, orientation and formation of the pressure-openable slit aperture  30  may vary, depending upon the desired predetermined maximum pressure P MAX  and predetermined closing pressure P CLS . In the particular embodiment shown, the predetermined maximum pressure P MAX  which will cause the pressure-openable slit aperture  30  to open is a function of the thickness T of the wall of the tube, the width or thickness of the tool utilized to make the pressure-openable slit aperture  30  in the wall of the tube  12 , and the angle A of such slit aperture  30  relative to a radial line or ray R which is projectible at 90° to the longitudinal axis LA of the tube  12 . When the tool or instrument utilized to make the pressure-openable slit aperture  30  is of minimal width so as not to create a slit which is incapable of assuming a fully closed configuration, the factors which will determine the predetermined maximum pressure P MAX  at which the pressure-openable slit aperture  30  will open are a) the wall thickness T of the tube  12 , b) the angle A of the slit aperture  30  relative to the transverse axis (e.g., radius line R) of the tube  12 , c) the length L of the slit aperture  30 , and d) the internal diameter ID of the tube. With respect to the angle A of the slit aperture  30  relative to the radial line or ray R of the tube, it is to be appreciated that in embodiments such as that shown in  FIG. 4  wherein the lumen  14  of the tube  12  is round, the slit aperture  30  will form angle A relative to a radius line R which is projected from the inner end of the slit aperture  30  to the centerpoint of the round lumen  14 . However, various alternative configurations may be employed wherein the lumen  14  of the tube is other than round, and in such alternative configurations the angle A of the slit aperture  30  will be defined relative to a transverse axis projected from the inner end of the slit aperture  30  to a centerpoint or center-of-flow point within the lumen  14  of the tube  12 . In either instance, the angle A of the slit aperture  30  relative to such radial line or ray R will determine the amount of tube material which the slit aperture  30  must penetrate through, thereby determining at least in part the amount of fluid pressure which will be required to spread apart the adjacent sides of the slit aperture  30  to cause opening of the slit aperture  30 . For example, with reference to the showing of  FIG. 4 , if the slit aperture  30  were to extend straight through the wall of the tube  12 , the angle A would be 180°, and the slit aperture  30  would pass through the minimum amount of tubular material determined by the wall thickness of the tube  12 . However, as the angle A decreases from 180° to 90°, the amount of tubular material through which the slit aperture  30  must pass will increase, thereby requiring greater pressure to part the opposite sides of the slit aperture  30  to accomplish opening thereof. Thus, it is in this manner that the angle A of the slit aperture  30  relative to the radial line or ray R of the tube  12  will function as one of the variables which are determinative of the predetermined maximum pressure P MAX  and/or the predetermined closing pressure P CLS  of the slit aperture  30 .  
         [0044]     It will be appreciated that the tube  12  and diffusion chamber  20  may be formed of any material which is suitable for the particular application for which the device  10  is to be used. Examples of materials of which the tube  12  may be formed include, but are not necessarily limited to silicone, hydrogels, polyurethanes, polyesters, latex, natural rubbers, and, cellulosics. Examples of the materials of which the diffusion chamber may be formed include, but are not necessarily limited to, cellulose acetate, cellulosics, polyesters, polyfluorocarbons, hydrogels, polyolefins, a hydrogel made from at least one hydrophilic monomer and at least one olefinic/polyolefinic cross-linker, and, other natural polymers.  
         [0000]     ii. Application of the Invention for Glaucoma Treatment  
         [0045]     a. Implantantion of the Device to Control Intraoccular Pressure  
         [0046]      FIG. 5  shows the device of  FIG. 1 , implanted within the human eye for treatment of glaucoma the anatomical structures shown in  FIG. 5  are labeled in accordance with the following:  
                                                       Anterior Angle   AA           Anterior Chamber   AC           Ciliary Body   CB           Conjunctiva   CON           Cornea   COR           Iris   IR           Lens   L           Sclera   SC           Sinus Venosus Sclerae   SVS           Suspensory Ligaments   SL                        
         [0047]     In this application of the device the tube  12  will typically have an outer diameter of approximately 0.6 mm, an inner diameter of approximately 0.3 mm and a length of approximately 40-45 mm. The concave abutment flange  42  will be positioned approximately 5 mm from the distal end  16  of the tube  12 , and will have a height H of approximately 1 mm, a width W of approximately 3 mm and a depth D of approximately 1 mm.  
         [0048]     The shape of the concave abutment flange  42  may be other than circular, and preferably may be oval shape in the manner depicted in the figures. Such oval configuration of the concave abutment flange  42  will facilitate the desired passage of the flange  42  in a collapsed configuration through the opening formed into the anterior chamber AC of the eye, and will thereafter permit the fully deployed and uncollapsed flange  42  to properly seat or nest within the peripheral corner of the anterior chamber AC, in the manner shown in  FIG. 5 .  
         [0049]     As shown, the diffusion chamber  20  and proximal portion of the tube  12  are implanted in a cavity formed between the conjunctiva CON and sclera SC, on the lateral aspect of the ocular bulb. The diffusion chamber  20  may be doubled over or folded to facilitate insertion through a relatively small incisions and may subsequently be opened or unfolded while in the surgically-created pocket of tissue formed between the conjunctiva CON and sclera SC. The distal end  16  of the tube is advanced through an opening formed in the sclera, inboard of the sinus venosus sclerae SVS. The concave abutment flange  42  is passed through the surgically formed opening in the sclera and is retracted so as to be in firm abutment with the sclera and/or adjacent tissue, thereby maintaining the tube  12  in its desired longitudinal position with the appropriate length of tube  12  extending into the anterior chamber AC. Suture tab  38  is secured to the adjacent tissue of the conjunctiva CON by way of sutures, thereby affixing the distal portion of the tube  12  in its desired position, and maintaining the concave abutment flange  42  in contact with the sclera and/or adjacent tissue as described hereabove.  
         [0050]     If necessary or desirable, the diffusion chamber  20  of the device  10  may be initially secured within its desired implantation position by passing sutures through the suture-receiving apertures  36 , as shown. Following implantation, tissue will ingrow through tissue ingrowth apertures  34  to further facilitate anchoring and attachment of the diffusion chamber  20  to the surrounding tissue of the conjunctiva CON and sclera SC. Thus, with the device  10  implanted within the eye in the manner shown in  FIG. 5 , excess aqueous humor in the anterior chamber AC will enter the open distal end  16  of the tube  12 , and will flow through the lumen  14  of the tube  12 . When the pressure of aqueous humor within the lumen  14  of the tube  12  exceeds the predetermined maximum pressure P MAX  the pressure-openable slit aperture  30  will be caused to open, thereby allowing the access humor to flow out into the inner cavity  26  of the diffusion chamber  20 . Such outflow of aqueous humor will continue until the pressure of aqueous humor within the lumen  14  of the tube  12  falls below the predetermined closing pressure P CLS  of the pressure-openable slit aperture  30 , at which time the pressure-openable slit aperture  30  will once again assume its closed configuration. Thereafter, the pressure-openable slit  30  will remain closed until such time as the pressure of aqueous humor within the lumen  14  of the tube  12  once again exceeds the predetermined maximum pressure P MAX .  
         [0051]     For many glaucoma patients, the desired predetermined maximum pressure P MAX  will be approximately 15 mm/Hg, and the desired closing pressure P CLS  of the pressure-openable slit aperture  30  will be approximately 5 mm/Hg. As explained hereabove, the length and angular orientation of the pressure-openable slit apertures  30  will be adjusted to provide these desired predetermined maximum pressure P MAX  and predetermined closing pressure P CLS . In this regard, the pressure of aqueous humor within the anterior chamber AC of the eye will be prevented from exceeding the predetermined maximum pressure P MAX  of approximately 15 mm/Hg, and will also be prevented from falling below the predetermined closing pressure P CLS  of approximately 5 mm/Hg. Thus, in this application of the present invention, the device  10  will operate to maintain pressure of aqueous humor within the anterior chamber within the 5-20 mm/Hg range, and preferably in a range of approximately 5-15 mm/Hg.  
         [0052]     Excess aqueous humor which has passed through the tube  12  and into the inner cavity  26  of the diffusion chamber  20  will subsequently diffuse outwardly through the membrane walls  22   a,    22   b  of the chamber and into the surrounding tissue. Such fluid will, thereafter, be assimilated by normal physiological action of the tissues.  
         [0053]     In this glaucoma-treatment application, it is preferable that the membrane walls  22   a,    22   b  of the diffusion chamber  20  be formed of cellulose acetate and/or polyvinylidene fluoride (PVDF), as such materials exhibit desirable host tissue compatibility. This preferred membrane material will allow the aqueous humor which collects in the inner cavity  26  to diffuse outwardly therethrough, but will prevent cellular ingrowth, proteins or particulate matter from passing inwardly into the inner cavity  26  of the diffusion chamber  20  where such matter could a) block or interfere with the pressure-openable slit apertures  30  or b) migrate through the lumen  14  of the tube  12  into the anterior chamber AC of the eye.  
         [0054]     Also, in this glaucoma-treatment application, it is preferable that the tube  12  be formed of silicone.  
         [0055]     B. Sutureless Implantable Device for Controlling Intraoccular Pressure  
         [0056]      FIGS. 8-13  are directed to a sutureless embodiment  10   s  of the implantable fluid shunting device  10  described above. With specific reference to  FIGS. 8-11 , there is shown a sutureless implantable fluid shunting device  10   s  which comprises an elongate tube  12   s  having a lumen  14   s  extending longitudinally therethrough and a diffusion chamber  20   s  mounted on the proximal end thereof. The tube  12   s  has an open distal end  16   s,  a closed proximal end  18   s  and a pressure openable aperture  30   s  located in a proximal portion PP of the tube  12   s  which extends into the interior of the diffusion chamber  20   s.    
         [0057]     The diffusion chamber  20   s  is constructed of an upper membrane wall  22   sa  and lower membrane wall  22   sb.  The upper and lower membrane walls  22   sa,    22   sb  are sealed or connected to one another at their edges to form a sealed perimeter  24   s.  As shown, the tube  12   s  extends through a tube passage aperture  23   s  formed in the lower membrane wall  22   sb  of the diffusion chamber  20   s,  at an angle, such that an anterior portion of the diffusion chamber  20   s  overhangs the portion of the tube  12   s  which extends outside of the diffusion chamber&#39;s lower wall  22   sb.  As in the above-described suture-anchorable embodiment, the tube  12   s  of this device  10   s  is disposed such that the proximal portion PP of the tube  12   s  (i.e., the portion adjacent its proximal end  18   s ) extends into the inner cavity  26   s  of the diffusion chamber  20   s.  The portion of the lower membrane wall  22   sb  which surrounds the tube passage aperture  23   s  is sealed to the outer wall of the tube  12   s.  As a result, any fluid which flows through the tube  12   s  and into the inner cavity  26   s  of the diffusion chamber  20   s  will not freely leak therefrom.  
         [0058]     The diffusion chamber  20   s  is preferably formed of membranous material (e.g., permeable or semipermeable membrane material) which will permit the fluid which is desired to be drained by the tube  12   s  to flow from the inner cavity  26   s  of the diffusion chamber  20   s,  outwardly and into the region of the body wherein the diffusion chamber  20   s  is positioned, while preventing predetermined types of unwanted matter (e.g., proteins, solid particles which are greater than a predetermined size, etc.) from passing inwardly through such membrane and into the inner cavity  26   s  of the diffusion chamber  20   s.  Additionally, the material of the diffusion chamber  20   s  will prevent host cellular matter (e.g., tissues or cells such as fibroblasts, endothelium, epithelium, blood cells) from invading (e.g., ingrowing or migrating) the outer surface or inner lumen of the tube  12   s  and/or the inner cavity  26   s  of the diffusion chamber  20   s.    
         [0059]     The pressure-openable aperture  30   s  may comprise a pressure-openable slit aperture, as shown in  FIG. 9 . Such slit aperture  30   s  may be sized, configured, formed, located and operated in the same manner as the slit aperture  30  of the suture-anchorable device  10  shown in  FIGS. 1-3  and described hereabove.  
         [0060]     As illustrated in  FIG. 10 , the diffusion chamber  20   s  of this device  10   s  is specifically sized and shaped such that it may be positioned within a subconjuntival pocket which has been surgically formed in one superior quadrant of the eye, between the locations at which two (2) adjacent rectus muscles RM attach to the ocular bulb OB (e.g., between the attachment point AP of the lateral rectus muscle and the attachment point AP of the superior or inferior rectus muscle). The width W 1  of that portion of the diffusion chamber  20   s  which resides posterior to the attachment points AP of the adjacent rectus muscles RM between which the device  10   s  is implanted, is wider than the distance D between those muscle attachment points AP. Preferably, the width W 3  of that portion of the diffusion chamber  20   s  which resides anterior to those attachment points AP of the adjacent rectus muscles RM is also wider than the distance D between those muscle attachment points AP. The portion (i.e., the “inter-muscular” portion) of the diffusion chamber  20   s  which resides between the attachment points AP of the adjacent rectus muscles RM has a width W 2  which is at least slightly narrower than the distance D between those muscle attachment points AP. As a result, when the device  10   s  is implanted in the position shown in  FIG. 10 , it will be prevented from migrating in either lateral direction LD 1 , LD 2  by the abutment of the lateral sides of the diffusion chamber  20   s  against the attachment points AP of the rectus muscles RM. Additionally, the device  10   s  will be prevented from migrating in either the anterior direction AD or posterior direction PD by the abutment of the edges of the posterior portion (i.e., the portion of width W 1 ) and anterior portion (i.e., the portion of width W 3 ) of the diffusion chamber against the attachment points AP of the adjacent rectus muscles. Also, the device  10   s  is deterred from migrating in any direction by the engagement of the tube  12   s,  which extends downwardly through the lower wall  22   sb  of the diffusion chamber  20   s,  with the walls of the the puncture tract through which the tube extends from the subconjunctival pocket in which it is positioned, into the anterior chamber AC of the eye. Still further, the device  10   s  is prevented from migrating in the posterior direction PD by the bottoming out of the posterior portion of the diffusion chamber  20   s  against the posterior end of the surgically-formed subconjunctival pocket and/or the abutment of the anterior portion (i.e. the portion of width W 3 ) against the attachment points AP of the rectus muscles RM in instances where the width W 3  of that anterior portion AP of the diffusion chamber  20   s  is wider than the distance D between the muscle attachment points AP. In many applications, it may not be necessary for the anterior portion AP of the diffusion chamber  20   s  to be of a width W 3  which is wider than the distance D between the rectus muscle attachment points AP, as the potential for posterior migration of the device  10   s  may be adequately limited by a) the bottoming out of the posterior end of the diffusion chamber  20   s  against the posterior extent of the subconjunctival pocket and/or b) the lateral abutment of the tube  12   s  against the walls of the puncture tract through which that tube  12   s  extends into the anterior chamber AC. However, in cases where the subconjunctival pocket is deeper than necessary, or where it is otherwise deemed desirable to further restrict the posterior migration of the device  10   s,  the surgeon may select a device  10   s  which has an anterior portion of a width W 3  that is wider than the distance D between the rectus muscle attachment points AP, thereby providing for further prevention of undesirable migration in the posterior direction PD.  
         [0061]     It will be appreciated that the exact shape and dimensions of the diffusion chamber  20   s  may vary, while still incorporating the above-described configurational attributes which allow it to engage and be held in place by, the adjacent rectus muscle attachment points AP. For example,  FIG. 12  shows a diffusion chamber  20   s′  which, while still within the scope of the present invention, has a shape which is different from that shown in  FIGS. 8-11 .  
         [0062]     It will be further appreciated that this sutureless embodiment of the device  10   s  may be devoid on any suture passage apertures or suture tabs, as no sutures are required to be placed in the device  10   s  to hold it in place following implantation.  
         [0063]     C. A Preferred Technique for Implantation of the Sutureless Device in the Eye to Control Intraoccular Pressure  
         [0064]      FIG. 13  is a flow diagram showing the steps of a preferred technique for implanting the sutureless fluid shunting device  10   s  within the eye in the manner illustrated in  FIG. 10 .  
         [0000]     Step 1: Formation of Conjunctival Incision and Subconjunctival Pocket:  
         [0065]     A curved or straight incision IN of approximately 5 millimeters length is formed through the conjunctival layer, at the limbus. Thereafter, standard ophthalmological surgical technique is used to separate the conjunctival tissue from the underlying scleral tissue, thereby creating a subconjunctival pocket in a superior quadrant of the eye, posterior to the incision IN and between adjacent rectus muscles (e.g., between the superior rectus muscle RM and the lateral rectus muscle RM).  
         [0000]     Step 2: Insertion of the Implantable Fluid Shunting Device:  
         [0066]     With the diffusion chamber  20   s  of the device  10   s  in a collapsed (e.g., folded, rolled or compressed) state, the diffusion chamber  20   s  is inserted, posterior end first, through the incision IN and into the subconjunctival pocket. Thereafter, open (e.g., unfold, unroll or decompress) the diffusion chamber so that a) the inter-muscular portion of the diffusion chamber  20   s  of width W 2  resides between the attachment points AP of the adjacent rectus muscles RM, and b) the posterior portion of the diffusion chamber  20   s  of width W 1  resides posterior to the attachment points AP of rectus muscles RM.  
         [0000]     Step 3: Creation of Trans-Trabecular Puncture Tract:  
         [0067]     A needle or other puncturing member (e.g., a 23 gage needle) is then inserted through the incision IN and advanced, on a path which is substantially parallel to the iris, to create a puncture tract which extends from a location on the anterior scleral surface (i.e., the floor of the surgically formed subconjunctival pocket) approximately 1.5 millimeters proximal to the limbus into the anterior chamber AC. If necessary, a quantity of viscoelastic substance (e.g., hyaluronic acid or methyl cellulose) or other temporary embolization material may be deposited in the freshly-formed puncture tract to prevent backflow of aqueous humor from the anterior chamber and the possibility of resultant hypotony, while the tube  12   s  is being prepared for insertion through the puncture tract.  
         [0000]     Step 4: Insertion of Tube Into Anterior Chamber:  
         [0068]     The tube  12   s  is then inserted, distal end first, through the puncture tract until the distal end  16   s  of the tube enters the anterior chamber AC but does not touch the iris IR or corneal epithelium. The surgeon may trim the tube to length prior to insertion, to ensure that the distal end  16   s  of the tube  12   s  will reside at its desired position within the anterior chamber AC.  
         [0000]     Step 5: Closure of Conjunctival Incision:  
         [0069]     The small conjunctival incision IN is then closed by way of an absorbable suture or other suitable closure means (e.g, a polymer film which may be applied to the surface of the conjunctiva to hold the incision IN closed until healed).  
         [0070]     By the above-described five-step procedure, the implantable fluid shunting device  10   s  of the present invention may be surgically implanted in the eye, without the use of sutures (i.e., stitches, staples, clips, etc) to hold or anchor the device  10   s  at its desired position within the eye, relying instead on the engagement and interaction of the walls and/or edges of the diffusion chamber  20   s  and/ot tube  12   s  with the surrounding tissues, to hold the device  10   s  in its desired implantation position.  
         [0000]     iii. Application of the Invention for Treatment of Hydrocephalus  
         [0071]      FIG. 6  shows a variant of the device shown in  FIGS. 1-3 , implanted in the human body for treatment of hydrocephalus.  
         [0072]     In this application of the device  10 , the device  10  is devoid of the optional concave abutment flange  42 . The device  10  is implanted such that the diffusion chamber  20  is positioned within the peritoneum, and the tube  12  is passed subcutaneously over the thorax, neck and into the base of the skull. The distal portion of the tube  12  may reside in the space between the brain and cranium, or may be inserted into a ventricle of the vein in accordance with the applicable treatment technique for the particular case of hydrocephalus being treated. The optional suture tab  38  may be employed to anchor the tube  12  in its desired position within the cranial vault. Also, the suture passage apertures  34 ,  36  formed on the diffusion chamber  20  may be utilized to suture the diffusion chamber  20  in its desired position within the patients abdomen.  
         [0073]     When the device  10  has been implanted in the manner shown in  FIG. 6 , excess cerebrospinal fluid will enter the open distal end  16  of the tube  12  and will flow through the lumen  14  of the tube. When the cerebrospinal fluid pressure within the lumen  14  of the tube  12  exceeds the predetermined maximum pressure P MAX , the pressure-openable slits  30  will open, thereby allowing the excess cerebrospinal fluid flow into the inner cavity  26  of the diffusion chamber  20 . Such outflow of cerebrospinal fluid will continue until the pressure of cerebrospinal fluid within the lumen  14  of the tube  12  falls below the predetermined closing pressure P CLS .  
         [0074]     In many hydrocephalus patients, the desired predetermined maximum pressure P MAX , for treatment of hydrocephalus will be in the range of 10-20 mm/Hg, and the desired predetermined closing pressure P CLS  will be in the range of 0-10 mm/Hg. In this manner, the pressure of cerebrospinal fluid within the ventricle of the brain, or otherwise within the cranium, may be maintained in a prescribed range, such as a preferred range of 5-14 mm/Hg, in accordance with the particular predetermined P MAX  and P CLS  of the device  10 .  
         [0000]     iv. Alternative Configurations/Applications of the Invention  
         [0075]      FIGS. 7   a - 7   g  show alternative embodiments of the device  10   a - 10   g  wherein the diffusion chamber  20   a - 20   g  is of varying configuration, to facilitate use of the device  10 - 10   g  in various other applications.  
         [0076]     It will be appreciated that, the diffusive surface area of the diffusion chamber  20   a - 20   g  may be altered by changing the shape of the diffusion chamber  20 - 20   g.  Moreover, alterations or variations in the shape of the diffusion chamber  20 - 20   g,  especially those wherein openings or invaginations are formed in the diffusion chamber  20 - 20   g,  may form areas into which tissue may ingrow so as to soundly anchor and fix the diffusion chamber  20 - 20   g  within its desired implantation position. The utilization of indigenous tissue ingrowth as a means for physical fixation and anchoring of the diffusion chamber  20 - 20   g  is desirable in that it may eliminate the need for the use of permanent sutures for anchoring of the diffusion chamber  20 - 20   g,  as sutures may tend to exert physical stress or force upon the diffusion chamber  20 - 20   g  and/or adjacent tissue. Furthermore, promoting tissue ingrowth within specific regions of the diffusion chamber  20 - 20   g  may firmly anchor and hold the diffusion chamber  20 - 20   g  in its desired implantation position so as to deter or prevent post-surgical micromovement of the device  10 . In this regard, the embodiments illustrated in  FIGS. 7   a - 7   g  incorporate various modifications wherein multiple projections, invaginations, and other configurational variations are formed in the diffusion chamber  20   a - 20   g.    
         [0077]     Additionally, it will be appreciated that the shape of the diffusion chamber may be modified to facilitate a) folding of the diffusion chamber to facilitate its insertion into a specific area of the body and b) ease of placement and retention of the diffusion chamber  20   a - 20   g  at its intended site of implantation.  
         [0078]     The alternative embodiments shown in  FIGS. 7   a - 7   g  are merely examples of the multitude of shapes and configurations in which the diffusion chamber  20   a - 20   g  may be formed and, accordingly, the intended shape or configuration of the diffusion chamber  20  shall not be limited to only those shapes and configurations shown in the drawings, but shall include any and all other shapes or configurations in which the diffusion chamber  20  may be formed.  
         [0079]     In particular, the diffusion chambers  20   a,    20   e,    20   g  shown in  FIGS. 7   a,    7   e,  and  7   g,  respectively, have curved or tapered outer edges whereby the proximal end of the diffusion chambers  20   a,    20   e,    20   g  is narrower than its distal end, thereby facilitating easy extraction and removal of the diffusion chamber  20   a,    20   e,    20   g,  if and when such removal is desired.  
         [0080]     The invention has been described hereabove with reference to certain presently preferred embodiments, and no attempt has been made to describe all possible embodiments in which the invention may take physical form. Indeed, numerous modifications, additions, deletions and alterations may be made to the above-described embodiments without departing from the intended spirit and scope of the invention. Accordingly, it is intended that all such additions, deletions, modifications and alterations be included within the scope of the following claims.