Abstract:
Implants and methods for treating ocular disorders are disclosed. One implant has a tubular member, with inlet and outlet ends, and a cutting member connected thereto. The tubular member is configured to extend through eye tissue such that the inlet and outlet ends reside respectively in an anterior chamber and a physiologic outflow pathway of the eye. Desirably, the cutting member is configured to make an incision in the eye tissue for receiving at least a portion of the tubular member. One method involves introducing an implant, with proximal and distal ends, into the anterior chamber and penetrating eye tissue using an implant distal portion. The implant is advanced from the anterior chamber into the penetrated eye tissue to locate the distal and proximal ends respectively in the physiologic outflow pathway and the anterior chamber. Aqueous humor is conducted between the proximal and distal ends.

Description:
RELATED APPLICATIONS 
     This application is a divisional of U.S. patent application Ser. No. 11/598,542, filed Nov. 13, 2006, entitled IMPLANT AND METHODS THEREOF FOR TREATMENT OF OCULAR DISORDERS, which is a continuation of U.S. patent application Ser. No. 10/118,578, filed Apr. 8, 2002, entitled GLAUCOMA STENT AND METHODS THEREOF FOR GLAUCOMA TREATMENT, now U.S. Pat. No. 7,135,009 B2, issued Nov. 14, 2006, which claims the benefit of U.S. Provisional Application No. 60/281,973, filed Apr. 7, 2001, entitled GLAUCOMA SHUNT AND METHODS THEREOF FOR GLAUCOMA TREATMENT, the entire contents of which are hereby incorporated by reference herein. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The invention relates generally to medical devices and methods for reducing the intraocular pressure in an animal eye and, more particularly, to shunt type devices for permitting aqueous outflow from the eye&#39;s anterior chamber and associated methods thereof for the treatment of glaucoma. 
     2. Description of the Related Art 
     The human eye is a specialized sensory organ capable of light reception and able to receive visual images. The trabecular meshwork serves as a drainage channel and is located in anterior chamber angle formed between the iris and the cornea. The trabecular meshwork maintains a balanced pressure in the anterior chamber of the eye by draining aqueous humor from the anterior chamber. 
     About two percent of people in the United States have glaucoma. Glaucoma is a group of eye diseases encompassing a broad spectrum of clinical presentations, etiologies, and treatment modalities. Glaucoma causes pathological changes in the optic nerve, visible on the optic disk, and it causes corresponding visual field loss, resulting in blindness if untreated. Lowering intraocular pressure is the major treatment goal in all glaucomas. 
     In glaucomas associated with an elevation in eye pressure (intraocular hypertension), the source of resistance to outflow is mainly in the trabecular meshwork. The tissue of the trabecular meshwork allows the aqueous humor (“aqueous”) to enter Schlemm&#39;s canal, which then empties into aqueous collector channels in the posterior wall of Schlemm&#39;s canal and then into aqueous veins, which form the episcleral venous system. Aqueous humor is a transparent liquid that fills the region between the cornea, at the front of the eye, and the lens. The aqueous humor is continuously secreted by the ciliary body around the lens, so there is a constant flow of aqueous humor from the ciliary body to the eye&#39;s front chamber. The eye&#39;s pressure is determined by a balance between the production of aqueous and its exit through the trabecular meshwork (major route) or uveal scleral outflow (minor route). The trabecular meshwork is located between the outer rim of the iris and the back of the cornea, in the anterior chamber angle. The portion of the trabecular meshwork adjacent to Schlemm&#39;s canal (the juxtacanilicular meshwork) causes most of the resistance to aqueous outflow. 
     Glaucoma is grossly classified into two categories: closed-angle glaucoma, also known as angle closure glaucoma, and open-angle glaucoma. Closed-angle glaucoma is caused by closure of the anterior chamber angle by contact between the iris and the inner surface of the trabecular meshwork. Closure of this anatomical angle prevents normal drainage of aqueous humor from the anterior chamber of the eye. 
     Open-angle glaucoma is any glaucoma in which the angle of the anterior chamber remains open, but the exit of aqueous through the trabecular meshwork is diminished. The exact cause for diminished filtration is unknown for most cases of open-angle glaucoma. Primary open-angle glaucoma is the most common of the glaucomas, and it is often asymptomatic in the early to moderately advanced stage. Patients may suffer substantial, irreversible vision loss prior to diagnosis and treatment. However, there are secondary open-angle glaucomas which may include edema or swelling of the trabecular spaces (e.g., from corticosteroid use), abnormal pigment dispersion, or diseases such as hyperthyroidism that produce vascular congestion. 
     Current therapies for glaucoma are directed at decreasing intraocular pressure. Medical therapy includes topical ophthalmic drops or oral medications that reduce the production or increase the outflow of aqueous. However, these drug therapies for glaucoma are sometimes associated with significant side effects, such as headache, blurred vision, allergic reactions, death from cardiopulmonary complications, and potential interactions with other drugs. When drug therapy fails, surgical therapy is used. Surgical therapy for open-angle glaucoma consists of laser trabeculoplasty, trabeculectomy, and implantation of aqueous shunts after failure of trabeculectomy or if trabeculectomy is unlikely to succeed. Trabeculectomy is a major surgery that is widely used and is augmented with topically applied anticancer drugs, such as 5-flurouracil or mitomycin-C to decrease scarring and increase the likelihood of surgical success. 
     Approximately 100,000 trabeculectomies are performed on Medicare-age patients per year in the United States. This number would likely increase if the morbidity associated with trabeculectomy could be decreased. The current morbidity associated with trabeculectomy consists of failure (10-15%); infection (a life long risk of 2-5%); choroidal hemorrhage, a severe internal hemorrhage from low intraocular pressure, resulting in visual loss (1%); cataract formation; and hypotony maculopathy (potentially reversible visual loss from low intraocular pressure). 
     For these reasons, surgeons have tried for decades to develop a workable surgery for the trabecular meshwork. 
     The surgical techniques that have been tried and practiced are goniotomy/trabeculotomy and other mechanical disruptions of the trabecular meshwork, such as trabeculopuncture, goniophotoablation, laser trabecular ablation, and goniocurretage. These are all major operations and are briefly described below. 
     Goniotomy/Trabeculotomy: Goniotomy and trabeculotomy are simple and directed techniques of microsurgical dissection with mechanical disruption of the trabecular meshwork. These initially had early favorable responses in the treatment of open-angle glaucoma. However, long-term review of surgical results showed only limited success in adults. In retrospect, these procedures probably failed due to cellular repair and fibrosis mechanisms and a process of “filling in.” Filling in is a detrimental effect of collapsing and closing in of the created opening in the trabecular meshwork. Once the created openings close, the pressure builds back up and the surgery fails. 
     Trabeculopuncture: Q-switched Neodynium (Nd) YAG lasers also have been investigated as an optically invasive technique for creating full-thickness holes in trabecular meshwork. However, the relatively small hole created by this trabeculopuncture technique exhibits a filling-in effect and fails. 
     Goniophotoablation/Laser Trabecular Ablation: Goniophotoablation is disclosed by Berlin in U.S. Pat. No. 4,846,172 and involves the use of an excimer laser to treat glaucoma by ablating the trabecular meshwork. This was demonstrated not to succeed by clinical trial. Hill et al. used an Erbium:YAG laser to create full-thickness holes through trabecular meshwork (Hill et al., Lasers in Surgery and Medicine 11:341-346, 1991). This technique was investigated in a primate model and a limited human clinical trial at the University of California, Irvine. Although morbidity was zero in both trials, success rates did not warrant further human trials. Failure was again from filling in of surgically created defects in the trabecular meshwork by repair mechanisms. Neither of these is a viable surgical technique for the treatment of glaucoma. 
     Goniocurretage: This is an ab interno (from the inside), mechanically disruptive technique that uses an instrument similar to a cyclodialysis spatula with a microcurrette at the tip. Initial results were similar to trabeculotomy: it failed due to repair mechanisms and a process of filling in. 
     Although trabeculectomy is the most commonly performed filtering surgery, viscocanulostomy (VC) and non-penetrating trabeculectomy (NPT) are two new variations of filtering surgery. These are ab externo (from the outside), major ocular-procedures in which Schlemm&#39;s canal is surgically exposed by making a large and very deep scleral flap. In the VC procedure, Schlemm&#39;s canal is cannulated and viscoelastic substance injected (which dilates Schlemm&#39;s canal and the aqueous collector channels). In the NPT procedure, the inner wall of Schlemm&#39;s canal is stripped off after surgically exposing the canal. 
     Trabeculectomy, VC, and NPT involve the formation of an opening or hole under the conjunctiva and scleral flap into the anterior chamber, such that aqueous humor is drained onto the surface of the eye or into the tissues located within the lateral wall of the eye. These surgical operations are major procedures with significant ocular morbidity. When trabeculectomy, VC, and NPT are thought to have a low chance for success, a number of implantable drainage devices have been used to ensure that the desired filtration and outflow of aqueous humor through the surgical opening will continue. The risk of placing a glaucoma drainage device also includes hemorrhage, infection, and diplopia (double vision). 
     Examples of implantable shunts and surgical methods for maintaining an opening for the release of aqueous humor from the anterior chamber of the eye to the sclera or space beneath the conjunctiva have been disclosed in, for example, U.S. Pat. No. 6,059,772 to Hsia et al., and U.S. Pat. No. 6,050,970 to Baerveldt. 
     All of the above surgeries and variations thereof have numerous disadvantages and moderate success rates. They involve substantial trauma to the eye and require great surgical skill in creating a hole through the full thickness of the sclera into the subconjunctival space. The procedures are generally performed in an operating room and have a prolonged recovery time for vision. 
     The complications of existing filtration surgery have prompted ophthalmic surgeons to find other approaches to lowering intraocular pressure. 
     The trabecular meshwork and juxtacanilicular tissue together provide the majority of resistance to the outflow of aqueous and, as such, are logical targets for surgical removal in the treatment of open-angle glaucoma. In addition, minimal amounts of tissue are altered and existing physiologic outflow pathways are utilized. 
     As reported in Arch. Ophthalm. (2000) 118:412, glaucoma remains a leading cause of blindness, and filtration surgery remains an effective, important option in controlling the disease. However, modifying existing filtering surgery techniques in any profound way to increase their effectiveness appears to have reached a dead end. The article further states that the time has come to search for new surgical approaches that may provide better and safer care for patients with glaucoma. 
     Therefore, there is a great clinical need for a method of treating glaucoma that is faster, safer, and less expensive than currently available modalities. 
     SUMMARY OF THE INVENTION 
     The trabecular meshwork and juxtacanilicular tissue together provide the majority of resistance to the outflow of aqueous and, as such, are logical targets for surgical approach in the treatment of glaucoma. Various embodiments of glaucoma shunts are disclosed herein for aqueous to exit through the trabecular meshwork (major route) or uveal scleral outflow (minor route) or other route effective to reduce intraocular pressure (IOP). 
     Glaucoma surgical morbidity would greatly decrease if one were to bypass the focal resistance to outflow of aqueous only at the point of resistance, and to utilize remaining, healthy aqueous outflow mechanisms. This is in part because episcleral aqueous humor exerts a backpressure that prevents intraocular pressure from going too low, and one could thereby avoid hypotony. Thus, such a surgery would virtually eliminate the risk of hypotony-related maculopathy and choroidal hemorrhage. Furthermore, visual recovery would be very rapid, and the risk of infection would be very small, reflecting a reduction in incidence from 2-5% to about 0.05%. 
     Copending U.S. application Ser. No. 09/549,350, filed Apr. 14, 2000, entitled APPARATUS AND METHOD FOR TREATING GLAUCOMA, and copending U.S. application Ser. No. 09/704,276, filed Nov. 1, 2000, entitled GLAUCOMA TREATMENT DEVICE, disclose devices and methods of placing a trabecular shunt ab interno, i.e., from inside the anterior chamber through the trabecular meshwork, into Schlemm&#39;s canal. The entire contents of each one of these copending patent applications are hereby incorporated by reference herein. The invention encompasses both ab interno and ab externo glaucoma shunts or stents and methods thereof. 
     Techniques performed in accordance with aspects herein may be referred to generally as “trabecular bypass surgery.” Advantages of this type of surgery include lowering intraocular pressure in a manner which is simple, effective, disease site-specific, and can potentially be performed on an outpatient basis. 
     Generally, trabecular bypass surgery (TBS) creates an opening, a slit, or a hole through trabecular meshwork with minor microsurgery. TBS has the advantage of a much lower risk of choroidal hemorrhage and infection than prior techniques, and it uses existing physiologic outflow mechanisms. In some aspects, this surgery can potentially be performed under topical or local anesthesia on an outpatient basis with rapid visual recovery. To prevent “filling in” of the hole, a biocompatible elongated device is placed within the hole and serves as a stent. U.S. patent application Ser. No. 09/549,350, filed Apr. 14, 2000, the entire contents of which are hereby incorporated by reference herein, discloses trabecular bypass surgery. 
     As described in U.S. patent application. Ser. No. 09/549,350, filed Apr. 14, 2000, and U.S. application Ser. No. 09/704,276, filed Nov. 1, 2000, the entire contents each one of which are hereby incorporated by reference herein, a trabecular shunt or stent for transporting aqueous humor is provided. The trabecular stent includes a hollow, elongate tubular element, having an inlet section and an outlet section. The outlet section may optionally include two segments or elements, adapted to be positioned and stabilized inside Schlemm&#39;s canal. In one embodiment, the device appears as a “T” shaped device. 
     In one aspect of the invention, a delivery apparatus (or “applicator”) is used for placing a trabecular stent through a trabecular meshwork of an eye. Certain embodiments of such a delivery apparatus are disclosed in copending U.S. application Ser. No. 10/101,548 (Inventors: Gregory T. Smedley, Irvine, Calif., Morteza Gharib, Pasadena, Calif., Hosheng Tu, Newport Beach, Calif.), filed Mar. 18, 2002, entitled APPLICATOR AND METHODS FOR PLACING A TRABECULAR SHUNT FOR GLAUCOMA TREATMENT, and U.S. Provisional Application No. 60/276,609, filed Mar. 16, 2001, entitled APPLICATOR AND METHODS FOR PLACING A TRABECULAR SHUNT FOR GLAUCOMA TREATMENT, the entire contents of each one of which are hereby incorporated by reference herein. 
     The stent has an inlet section and an outlet section. The delivery apparatus includes a handpiece, an elongate tip, a holder and an actuator. The handpiece has a distal end and a proximal end. The elongate tip is connected to the distal end of the handpiece. The elongate tip has a distal portion and is configured to be placed through a corneal incision and into an anterior chamber of the eye. The holder is attached to the distal portion of the elongate tip. The holder is configured to hold and release the inlet section of the trabecular stent. The actuator is on the handpiece and actuates the holder to release the inlet section of the trabecular stent from the holder. When the trabecular stent is deployed from the delivery apparatus into the eye, the outlet section is positioned in substantially opposite directions inside Schlemm&#39;s canal. In one embodiment, a deployment mechanism within the delivery apparatus includes a push-pull type plunger. 
     Some aspects of the invention relate to devices for reducing intraocular pressure by providing outflow of aqueous from an anterior chamber of an eye. The device generally comprises an elongated tubular member and cutting means. The tubular member is adapted for extending through a trabecular meshwork of the eye. The tubular member generally comprises a lumen having an inlet port and at least one outlet port for providing a flow pathway. The cutting means is mechanically connected to or is an integral part of the tubular member for creating an incision in the trabecular meshwork for receiving at least a portion of the tubular member. 
     In one aspect, a self-trephining glaucoma stent is provided for reducing and/or balancing intraocular pressure in an eye. The stent generally comprises a snorkel and a curved blade. The snorkel generally comprises an upper seat for stabilizing said stent within the eye, a shank and a lumen. The shank is mechanically connected to the seat and is adapted for extending through a trabecular meshwork of the eye. The lumen extends through the snorkel and has at least one inlet flow port and at least one outlet flow port. The blade is mechanically connected to the snorkel. The blade generally comprises a cutting tip proximate a distal-most point of the blade for making an incision in the trabecular meshwork for receiving the shank. 
     Some aspects of the invention relate to methods of implanting a trabecular stent device in an eye. In one aspect, the device has a snorkel mechanically connected to a blade. The blade is advanced through a trabecular meshwork of the eye to cut the trabecular meshwork and form an incision therein. At least a portion of the snorkel is inserted in the incision to implant the device in the eye. 
     Some aspects provide a self-trephining glaucoma stent and methods thereof which advantageously allow for a “one-step” procedure in which the incision and placement of the stent are accomplished by a single device and operation. This desirably allows for a faster, safer, and less expensive surgical procedure. In any of the embodiments, fiducial markings, indicia, or the like and/or positioning of the stent device in a preloaded applicator may be used for proper orientation and alignment of the device during implantation. 
     Among the advantages of trabecular bypass surgery is its simplicity. The microsurgery may potentially be performed on an outpatient basis with rapid visual recovery and greatly decreased morbidity. There is a lower risk of infection and choroidal hemorrhage, and there is a faster recovery, than with previous techniques. 
     For purposes of summarizing the invention, certain aspects, advantages and novel features of the invention have been described herein above. Of course, it is to be understood that not necessarily all such advantages may be achieved in accordance with any particular embodiment of the invention. Thus, the invention may be embodied or carried out in a manner that achieves or optimizes one advantage or group of advantages as taught or suggested herein without necessarily achieving other advantages as may be taught or suggested herein. 
     All of these embodiments are intended to be within the scope of the invention herein disclosed. These and other embodiments of the invention will become readily apparent to those skilled in the art from the following detailed description of the preferred embodiments having reference to the attached figures, the invention not being limited to any particular preferred embodiment(s) disclosed. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Having thus summarized the general nature of the invention and some of its features and advantages, certain preferred embodiments and modifications thereof will become apparent to those skilled in the art from the detailed description herein having reference to the figures that follow, of which: 
         FIG. 1  is a coronal cross-sectional view of an eye; 
         FIG. 2  is an enlarged cross-sectional view of an anterior chamber angle of the eye of  FIG. 1 ; 
         FIG. 3  is a simplified partial view of an eye illustrating the implantation of a glaucoma stent having features and advantages in accordance with one embodiment of the invention; 
         FIG. 4  is a side elevation view of the stent of  FIG. 3 ; 
         FIG. 5  is a top plan view of the stent of  FIG. 3 ; 
         FIG. 6  is a bottom plan view of the stent of  FIG. 3 ; 
         FIG. 7  is a front end view of the stent of  FIG. 3  (along line  7 - 7  of  FIG. 4 ); 
         FIG. 8  is a rear end view of the stent of  FIG. 3  (along line  8 - 8  of  FIG. 4 ); 
         FIG. 9  is an enlarged top plan view of a cutting tip of the stent of  FIG. 3 ; 
         FIG. 10  is a top plan view of one exemplary embodiment of a snorkel top seating surface; 
         FIG. 11  is a top plan view of another exemplary embodiment of a snorkel top seating surface; 
         FIG. 12  is a top plan view of yet another exemplary embodiment of a snorkel top seating surface; 
         FIG. 13  is a top plan view of still another exemplary embodiment of a snorkel top seating surface; 
         FIG. 14  is a simplified partial view of an eye illustrating the implantation of a glaucoma stent having features and advantages in accordance with another embodiment of the invention; 
         FIG. 15  is a simplified partial view of an eye illustrating the implantation of a glaucoma stent having features and advantages in accordance with a further embodiment of the invention; 
         FIG. 16  is a side elevation view of a glaucoma stent having features and advantages in accordance with one embodiment of the invention; 
         FIG. 17  is a top plan view of the stent of  FIG. 16 ; 
         FIG. 18  is a bottom plan view of the stent of  FIG. 16 ; 
         FIG. 19  is a front end view along line  19 - 19  of  FIG. 16 ; 
         FIG. 20  is a rear end view along line  20 - 20  of  FIG. 16 ; 
         FIG. 21  is a side elevation view of a glaucoma stent having features and advantages in accordance with one embodiment of the invention; 
         FIG. 22  is a top plan view of the stent of  FIG. 21 ; 
         FIG. 23  is a bottom plan view of the stent of  FIG. 21 ; 
         FIG. 24  is a front end view along line  24 - 24  of  FIG. 21 ; 
         FIG. 25  is a rear end view along line  25 - 25  of  FIG. 21 ; 
         FIG. 26  is a front elevation view of a glaucoma stent having features and advantages in accordance with one embodiment of the invention; 
         FIG. 27  is a side elevation view along line  27 - 27  of  FIG. 26 ; 
         FIG. 28  is a rear end view along line  28 - 28  of  FIG. 26 ; 
         FIG. 29  is a simplified partial view of an eye illustrating the temporal implantation of a glaucoma stent using a delivery apparatus having features and advantages in accordance with one embodiment of the invention; 
         FIG. 30  is an oblique elevational view of an articulating arm stent delivery/retrieval apparatus having features and advantages in accordance with one embodiment of the invention; 
         FIG. 31  is a simplified partial view of an eye illustrating the implantation of a glaucoma stent using a delivery apparatus crossing through the eye anterior chamber; 
         FIG. 32  is a simplified partial view of an eye illustrating the implantation of a glaucoma stent having features and advantages in accordance with one embodiment of the invention; 
         FIG. 33  is a detailed enlarged view of the barbed pin of  FIG. 32 ; 
         FIG. 34  is a simplified partial view of an eye illustrating the implantation of a glaucoma stent having features and advantages in accordance with one embodiment of the invention; 
         FIG. 35  is a simplified partial view of an eye illustrating the implantation of a glaucoma stent having features and advantages in accordance with one embodiment of the invention; 
         FIG. 36  is a simplified partial view of an eye illustrating the implantation of a glaucoma stent having features and advantages in accordance with one embodiment of the invention; 
         FIG. 37  is a simplified partial view of an eye illustrating the implantation of a glaucoma stent having features and advantages in accordance with one embodiment of the invention; 
         FIG. 38  is a simplified partial view of an eye illustrating the implantation of a glaucoma stent having features and advantages in accordance with one embodiment of the invention; 
         FIG. 39  is a simplified partial view of an eye illustrating the implantation of a glaucoma stent having features and advantages in accordance with one embodiment of the invention; 
         FIG. 40  is a simplified partial view of an eye illustrating the implantation of a glaucoma stent having features and advantages in accordance with one embodiment of the invention; 
         FIG. 41  is a simplified partial view of an eye illustrating the implantation of a glaucoma stent having features and advantages in accordance with one embodiment of the invention; 
         FIG. 42  is a simplified partial view of an eye illustrating the implantation of a glaucoma stent having features and advantages in accordance with one embodiment of the invention; 
         FIG. 43  is a simplified partial view of an eye illustrating the implantation of a valved tube stent device having features and advantages in accordance with one embodiment of the invention; 
         FIG. 44  is a simplified partial view of an eye illustrating the implantation of an osmotic membrane device having features and advantages in accordance with one embodiment of the invention; 
         FIG. 45  is a simplified partial view of an eye illustrating the implantation of a glaucoma stent using ab externo procedure having features and advantages in accordance with one embodiment of the invention; 
         FIG. 46  is a simplified partial view of an eye illustrating the implantation of a glaucoma stent having features and advantages in accordance with a modified embodiment of the invention; and 
         FIG. 47  is a simplified partial view of an eye illustrating the implantation of a drug release implant having features and advantages in accordance with one embodiment of the invention. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The preferred embodiments of the invention described herein relate particularly to surgical and therapeutic treatment of glaucoma through reduction of intraocular pressure. While the description sets forth various embodiment specific details, it will be appreciated that the description is illustrative only and should not be construed in any way as limiting the invention. Furthermore, various applications of the invention, and modifications thereto, which may occur to those who are skilled in the art, are also encompassed by the general concepts described herein. 
       FIG. 1  is a cross-sectional view of an eye  10 , while  FIG. 2  is a close-up view showing the relative anatomical locations of a trabecular meshwork  21 , an anterior chamber  20 , and Schlemm&#39;s canal  22 . A sclera  11  is a thick collagenous tissue which covers the entire eye  10  except a portion which is covered by a cornea  12 . 
     Referring to  FIGS. 1 and 2 , the cornea  12  is a thin transparent tissue that focuses and transmits light into the eye and through a pupil  14 , which is a circular hole in the center of an iris  13  (colored portion of the eye). The cornea  12  merges into the sclera  11  at a juncture referred to as a limbus  15 . A ciliary body  16  extends along the interior of the sclera  11  and is coextensive with a choroid  17 . The choroid  17  is a vascular layer of the eye  10 , located between the sclera  11  and a retina  18 . An optic nerve  19  transmits visual information to the brain and is the anatomic structure that is progressively destroyed by glaucoma. 
     Still referring to  FIGS. 1 and 2 , the anterior chamber  20  of the eye  10 , which is bound anteriorly by the cornea  12  and posteriorly by the iris  13  and a lens  26 , is filled with aqueous humor (hereinafter referred to as “aqueous”). Aqueous is produced primarily by the ciliary body  16 , then moves anteriorly through the pupil  14  and reaches an anterior chamber angle  25 , formed between the iris  13  and the cornea  12 . 
     As best illustrated by the drawing of  FIG. 2 , in a normal eye, aqueous is removed from the anterior chamber  20  through the trabecular meshwork  21 . Aqueous passes through the trabecular meshwork  21  into Schlemm&#39;s canal  22  and thereafter through a plurality of aqueous veins  23 , which merge with blood-carrying veins, and into systemic venous circulation. Intraocular pressure is maintained by an intricate balance between secretion and outflow of aqueous in the manner described above. Glaucoma is, in most cases, characterized by an excessive buildup of aqueous in the anterior chamber  20  which leads to an increase in intraocular pressure. Fluids are relatively incompressible, and thus intraocular pressure is distributed relatively uniformly throughout the eye  10 . 
     As shown in  FIG. 2 , the trabecular meshwork  21  is adjacent a small portion of the sclera  11 . Exterior to the sclera  11  is a conjunctiva  24 . Traditional procedures that create a hole or opening for implanting a device through the tissues of the conjunctiva  24  and sclera  11  involve extensive surgery by an ab externo procedure, as compared to surgery for implanting a device, as described herein, which ultimately resides entirely within the confines of the sclera  11  and cornea  12 . 
     Self-Trephining Glaucoma Stent 
       FIG. 3  generally illustrates the use of one embodiment of a trabecular stenting device  30  for establishing an outflow pathway, passing through the trabecular meshwork  21 , which is discussed in greater detail below.  FIGS. 4-9  are different views of the stent  30 . Advantageously, and as discussed in further detail later herein, the self-trephining-stent allows a one-step procedure to make an incision in the trabecular mesh  21  and place the stent or implant  30  at the desired or predetermined position within the eye  10 . Desirably, this facilitates and simplifies the overall surgical procedure. 
     In the illustrated embodiment of  FIGS. 3-9 , the shunt or stent  30  generally comprises a snorkel  32  and a main body portion or blade  34 . The snorkel  32  and blade  34  are mechanically connected to or in mechanical communication with one another. The stent  30  and/or the body portion  34  have a generally longitudinal axis  36 . 
     In the illustrated embodiment of  FIGS. 3-9 , the stent  30  comprises an integral unit. In modified embodiments, the stent  30  may comprise an assembly of individual pieces or components. For example, the stent  30  may comprise an assembly of the snorkel  32  and blade  34 . 
     In the illustrated embodiment of  FIGS. 3-9 , the snorkel  32  is in the form of a generally elongate tubular member and generally comprises an upper seat, head or cap portion  38 , a shank portion  40  and a lumen or passage  42  extending therethrough. The seat  38  is mechanically connected to or in mechanical communication with the shank  40  which is also mechanically connected to or in mechanical communication with the blade  34 . The snorkel  32  and/or the lumen  42  have a generally longitudinal axis  43 . 
     In the illustrated embodiment of  FIGS. 3-9 , the seat  38  is generally circular in shape and has an upper surface  44  and a lower surface  46  which, as shown in  FIG. 3 , abuts or rests against the trabecular meshwork  21  to stabilize the glaucoma stent  30  within the eye  10 . In modified embodiments, the seat  38  may efficaciously be shaped in other suitable manners, as required or desired, giving due consideration to the goals of stabilizing the glaucoma stent  30  within the eye  10  and/or of achieving one or more of the benefits and advantages as taught or suggested herein. For example, the seat  38  may be shaped in other polygonal or non-polygonal shapes and/or comprise one or more ridges which extend radially outwards, among other suitable retention devices. 
     In the illustrated embodiment of  FIGS. 3-9 , and as best seen in the top view of  FIG. 5 , the seat top surface  44  comprises fiducial marks or indicia  48 . These marks or indicia  48  facilitate and ensure proper orientation and alignment of the stent  30  when implanted in the eye  10 . The marks or indicia  48  may comprise visual differentiation means such as color contrast or be in the form of ribs, grooves, or the like. Alternatively, or in addition, the marks  48  may provide tactile sensory feedback to the surgeon by incorporating a radiopaque detectable or ultrasound imaginable substrate at about the mark  48 . Also, the seat  38  and/or the seat top surface  44  may be configured in predetermined shapes aligned with the blade  34  and/or longitudinal axis  36  to provide for proper orientation of the stent device  30  within the eye  10 . For example, the seat top surface  44  may be oval or ellipsoidal ( FIG. 10 ), rectangular ( FIG. 11 ), hexagonal ( FIG. 12 ), among other suitable shapes (e.g.  FIG. 13 ). 
     In the illustrated embodiment of  FIGS. 3-9 , and as indicated above, the seat bottom surface  46  abuts or rests against the trabecular meshwork  21  to stabilize and retain the glaucoma stent  30  within the eye  10 . For stabilization purposes, the seat bottom surface  46  may comprise a stubbed surface, a ribbed surface, a surface with pillars, a textured surface, or the like. 
     In the illustrated embodiment of  FIGS. 3-9 , the snorkel shank  40  is generally cylindrical in shape. With the stent  30  implanted, as shown in  FIG. 3 , the shank  40  is generally positioned in an incision or cavity  50  formed in the trabecular meshwork  21  by the self-trephining stent  30 . Advantageously, and as discussed further below, this single step of forming the cavity  50  by the stent  30  itself and placing the stent  30  in the desired position facilitates and expedites the overall surgical procedure. In modified embodiments, the snorkel shank  40  may efficaciously be shaped in other suitable manners, as required or desired. For example, the shank  40  may be in the shape of other polygonal or non-polygonal shapes, such as, oval, ellipsoidal, and the like. 
     In the illustrated embodiment of  FIGS. 3-9 , and as best seen in  FIG. 3 , the shank  40  has an outer surface  52  in contact with the trabecular meshwork  21  surrounding the cavity  50 . For stabilization purposes, the shank outer surface  52  may comprise a stubbed surface, a ribbed surface, a surface with pillars, a textured surface, or the like. 
     In the illustrated embodiment of  FIGS. 3-9 , the snorkel lumen  42  has an inlet port, opening or orifice  54  at the seat top surface  44  and an outlet port, opening or orifice  56  at the junction of the shank  40  and blade  34 . The lumen  42  is generally cylindrical in shape, that is, it has a generally circular cross-section, and its ports  54 ,  56  are generally circular in shape. In modified embodiments, the lumen  42  and ports  54 ,  56  may be efficaciously shaped in other manners, as required or desired, giving due consideration to the goals of providing sufficient aqueous outflow and/or of achieving one or more of the benefits and advantages as taught or suggested herein. For example, the lumen  42  and/or one or both ports  54 ,  56  may be shaped in the form of ovals, ellipsoids, and the like, or the lumen  42  may have a tapered or stepped configuration. 
     Referring in particular to  FIG. 3 , aqueous from the anterior chamber  20  flows into the lumen  42  through the inlet port  54  (as generally indicated by arrow  58 ) and out of the outlet port  56  and into Schlemm&#39;s canal  22  (as generally indicated by arrows  60 ) to lower and/or balance the intraocular pressure (IOP). In another embodiment, as discussed in further detail below, one or more of the outlet ports may be configured to face in the general direction of the stent longitudinal axis  36 . In modified embodiments, the snorkel  32  may comprise more than one lumen, as needed or desired, to facilitate multiple aqueous outflow transportation into Schlemm&#39;s canal  22 . 
     In the illustrated embodiment of  FIGS. 3-9 , the blade longitudinal axis  36  and the snorkel longitudinal axis  43  are generally perpendicular to one another. Stated differently, the projections of the axes  36 ,  43  on a common plane which is not perpendicular to either of the axes  36 ,  43  intersect at 90°. The blade longitudinal axis  36  and the snorkel longitudinal axis  43  may intersect one another or may be offset from one another. 
     In the illustrated embodiment of  FIGS. 3-9 , the main body portion or blade  34  is a generally curved elongated sheet- or plate-like structure with an upper curved surface  62  and a lower curved surface  64  which defines a trough or open face channel  66 . The perimeter of the blade  34  is generally defined by a curved proximal edge  68  proximate to the snorkel  32 , a curved distal edge  70  spaced from the proximal edge  68  by a pair of generally straight lateral edges  72 ,  74  with the first lateral edge  72  extending beyond the second lateral edge  74  and intersecting with the distal edge  70  at a distal-most point  76  of the blade  34  proximate a blade cutting tip  78 . 
     In the illustrated embodiment of  FIGS. 3-9 , and as shown in the enlarged view of  FIG. 9 , the cutting tip  78  comprises a first cutting edge  80  on the distal edge  70  and a second cutting edge  82  on the lateral edge  72 . The cutting edges  80 ,  82  preferably extend from the distal-most point  76  of the blade  34  and comprise at least a respective portion of the distal edge  70  and lateral edge  72 . The respective cutting edges  80 ,  82  are formed at the sharp edges of respective beveled or tapered surfaces  84 ,  86 . In one embodiment, the remainder of the distal edge  70  and lateral edge  72  are dull or rounded. In one embodiment, the tip  78  proximate to the distal-most end  76  is curved slightly inwards, as indicated generally by the arrow  88  in  FIG. 5  and arrow  88  (pointed perpendicular and into the plane of the paper) in  FIG. 9 , relative to the adjacent curvature of the blade  34 . 
     In modified embodiments, suitable cutting edges may be provided on selected portions of one or more selected blade edges  68 ,  70 ,  72 ,  74  with efficacy, as needed or desired, giving due consideration to the goals of providing suitable cutting means on the stent  30  for effectively cutting through the trabecular meshwork  21  ( FIG. 3 ) and/or of achieving one or more of the benefits and advantages as taught or suggested herein. 
     Referring in particular to  FIG. 9 , in one embodiment, the ratio between the lengths of the cutting edges  80 ,  82  is about 2:1. In another embodiment, the ratio between the lengths of the cutting edges  80 ,  82  is about 1:1. In yet another embodiment, the ratio between the lengths of the cutting edges  80 ,  82  is about 1:2. In modified embodiments, the lengths of the cutting edges  80 ,  82  may be efficaciously selected in other manners, as required or desired, giving due consideration to the goals of providing suitable cutting means on the stent  30  for effectively cutting through the trabecular meshwork  21  ( FIG. 3 ) and/or of achieving one or more of the benefits and advantages as taught or suggested herein. 
     Still referring in particular to  FIG. 9 , in one embodiment, the ratio between the lengths of the cutting edges  80 ,  82  is in the range from about 2:1 to about 1:2. In another embodiment, the ratio between the lengths of the cutting edges  80 ,  82  is in the range from about 5:1 to about 1:5. In yet another embodiment, the ratio between the lengths of the cutting edges  80 ,  82  is in the range from about 10:1 to about 1:10. In modified embodiments, the lengths of the cutting edges  80 ,  82  may be efficaciously selected in other manners, as required or desired, giving due consideration to the goals of providing suitable cutting means on the stent  30  for effectively cutting through the trabecular meshwork  21  ( FIG. 3 ) and/or of achieving one or more of the benefits and advantages as taught or suggested herein. 
     As shown in the top view of  FIG. 9 , the cutting edge  80  (and/or the distal end  70 ) and the cutting edge  82  (and/or the lateral edge  72 ) intersect at an angle θ. Stated differently, θ is the angle between the projections of the cutting edge  80  (and/or the distal end  70 ) and the cutting edge  82  (and/or the lateral edge  72 ) on a common plane which is not perpendicular to either of these edges. 
     Referring to in particular to  FIG. 9 , in one embodiment, the angle θ is about 50°. In another embodiment, the angle θ is in the range from about 40° to about 60°. In yet another embodiment, the angle θ is in the range from about 30° to about 70°. In modified embodiments, the angle θ may be efficaciously selected in other manners, as required or desired, giving due consideration to the goals of providing suitable cutting means on the stent  30  for effectively cutting through the trabecular meshwork  21  ( FIG. 3 ) and/or of achieving one or more of the benefits and advantages as taught or suggested herein. 
     The stent  30  of the embodiments disclosed herein can be dimensioned in a wide variety of manners. Referring in particular to  FIG. 3 , the depth of Schlemm&#39;s canal  22  is typically about less than 400 microns (μm). Accordingly, the stunt blade  34  is dimensioned so that the height of the blade  34  (referred to as H 41  in  FIG. 4 ) is typically less than about 400 μm. The snorkel shank  40  is dimensioned so that it has a length (referred to as L 41  in  FIG. 4 ) typically in the range from about 150 μm to about 400 μm which is roughly the typical range of the thickness of the trabecular meshwork  21 . 
     Of course, as the skilled artisan will appreciate, that with the stent  30  implanted, the blade  34  may rest at any suitable position within Schlemm&#39;s canal  22 . For example, the blade  34  may be adjacent to a front wall  90  of Schlemm&#39;s canal  22  (as shown in  FIG. 3 ), or adjacent to a back wall  92  of Schlemm&#39;s canal  22 , or at some intermediate location therebetween, as needed or desired. Also, the snorkel shank  40  may extend into Schlemm&#39;s canal  22 . The length of the snorkel shank  40  and/or the dimensions of the blade  34  may be efficaciously adjusted to achieve the desired implant positioning. 
     The trabecular stenting device  30  ( FIGS. 3-9 ) of the exemplary embodiment may be manufactured or fabricated by a wide variety of techniques. These include, without limitation, by molding, thermo-forming, or other micro-machining techniques, among other suitable techniques. 
     The trabecular stenting device  30  preferably comprises a biocompatible material such that inflammation arising due to irritation between the outer surface of the device  30  and the surrounding tissue is minimized. Biocompatible materials which may be used for the device  30  preferably include, but are not limited to, titanium, titanium alloys, medical grade silicone, e.g., Silastic™, available from Dow Corning Corporation of Midland, Mich.; and polyurethane, e.g., Pellethane™, also available from Dow Corning Corporation. 
     In other embodiments, the stent device  30  may comprise other types of biocompatible material, such as, by way of example, polyvinyl alcohol, polyvinyl pyrolidone, collagen, heparinized collagen, polytetrafluoroethylene, expanded polytetrafluoroethylene, fluorinated polymer, fluorinated elastomer, flexible fused silica, polyolefin, polyester, polysilicon, and/or a mixture of the aforementioned biocompatible materials, and the like. In still other embodiments, composite biocompatible material may be used, wherein a surface material may be used in addition to one or more of the aforementioned materials. For example, such a surface material may include polytetrafluoroethylene (PTFE) (such as Teflon™), polyimide, hydrogel, heparin, therapeutic drugs (such as beta-adrenergic antagonists and other anti-glaucoma drugs, or antibiotics), and the like. 
     In an exemplary embodiment of the trabecular meshwork surgery, the patient is placed in the supine position, prepped, draped and anesthetized as necessary. In one embodiment, a small (less than about 1 mm) incision, which may be self sealing is made through the cornea  12 . The corneal incision can be made in a number of ways, for example, by using a micro-knife, among other tools. 
     An applicator or delivery apparatus is used to advance the glaucoma stent  30  through the corneal incision and to the trabecular meshwork  21 . Some embodiments of such a delivery apparatus are disclosed in copending U.S. application Ser. No. 10/101,548 (Inventors: Gregory T. Smedley, Irvine, Calif., Morteza Gharib, Pasadena, Calif., Hosheng Tu, Newport Beach, Calif.), filed Mar. 18, 2002, entitled APPLICATOR AND METHODS FOR PLACING A TRABECULAR SHUNT FOR GLAUCOMA TREATMENT, and U.S. Provisional Application No. 60/276,609, filed Mar. 16, 2001, entitled APPLICATOR AND METHODS FOR PLACING A TRABECULAR SHUNT FOR GLAUCOMA TREATMENT, the entire contents of each one of which are hereby incorporated by reference herein. Some embodiments of a delivery apparatus are also discussed in further detail later herein. Gonioscopic, microscopic, or endoscopic guidance may be used during the trabecular meshwork surgery. 
     With the device  30  held by the delivery apparatus, the blade  34  of the self-trephining glaucoma stent device  30  is used to cut and/or displace the material of the trabecular meshwork  21 . The snorkel shank  40  may also facilitate in removal of this material during implantation. The delivery apparatus is withdrawn once the device  30  has been implanted in the eye  10 . As shown in  FIG. 3 , once proper implantation has been accomplished the snorkel seat  38  rests on a top surface  94  of the trabecular meshwork  21 , the snorkel shank  40  extends through the cavity  50  (created by the device  30 ) in the trabecular meshwork  21 , and the blade extends inside Schlemm&#39;s canal  22 . 
     Advantageously, the embodiments of the self-trephining stent device of the invention allow for a “one-step” procedure to make an incision in the trabecular meshwork and to subsequently implant the stent in the proper orientation and alignment within the eye to allow outflow of aqueous from the anterior chamber through the stent and into Schlemm&#39;s canal to lower and/or balance the intraocular pressure (IOP). Desirably, this provides for a faster, safer, and less expensive surgical procedure. 
     Many complications can arise in trabecular meshwork surgeries, wherein a knife is first used to create an incision in the trabecular meshwork, followed by removal of the knife and subsequent installation of the stent. For instance, the knife may cause some bleeding which clouds up the surgical site. This may require more effort and time to clean the surgical site prior to placement of the stent. Moreover, this may cause the intraocular pressure (IOP) to rise or to fall undesirably. Thus, undesirably, such a multiple step procedure may demand crisis management which slows down the surgery, makes it less safe, and more expensive. 
       FIG. 14  is a simplified partial view of an eye  10  illustrating the implantation of a self-trephining glaucoma stent device  30   a  having features and advantages in accordance with one embodiment. The stent  30   a  is generally similar to the stent  30  of  FIGS. 3-9  except that its snorkel  32   a  comprises a longer shank  40   a  which extends into Schlemm&#39;s canal  22  and a lumen  42   a  which bifurcates into two output channels  45   a.    
     In the illustrated embodiment of  FIG. 14 , the shank  40   a  terminates at the blade  34 . Aqueous flows from the anterior chamber  20  into the lumen  42   a  through an inlet port  54   a  (as generally indicated by arrow  58   a ). Aqueous then flows through the output channels  45   a  and out of respective outlet ports  56   a  and into Schlemm&#39;s canal  22  (as generally indicated by arrows  60   a ). The outlet channels  45   a  extend radially outwards in generally opposed directions and the outlet ports  56   a  are configured to face in the general direction of the stent longitudinal axis  36  so that they open into Schlemm&#39;s canal  22  and are in proper orientation to allow aqueous outflow into Schlemm&#39;s canal  22  for lowering and/or balancing the intraocular pressure (IOP). As indicated above, fiducial marks or indicia and/or predetermined shapes of the snorkel seat  38  allow for proper orientation of the blade  34  and also the output channels  45   a  and respective ports  56   a  within Schlemm&#39;s canal. 
     In the illustrated embodiment of  FIG. 14 , two outflow channels  45   a  are provided. In another embodiment, only one outflow channel  45   a  is provided. In yet another embodiment, more than two outflow channels  45   a  are provided. In modified embodiments, the lumen  42   a  may extend all the way through to the blade  34  and provide an outlet port as discussed above with reference to the embodiment of  FIGS. 3-9 . 
       FIG. 15  is a simplified partial view of an eye  10  illustrating the implantation of a self-trephining glaucoma stent device  30   b  having features and advantages in accordance with one embodiment. The stent  30   b  is generally similar to the stent  30  of  FIGS. 3-9  except that its snorkel  32   b  comprises a longer shank  40   b  which extends into Schlemm&#39;s canal  22  and a lumen  42   b  which bifurcates into two output channels  45   b.    
     In the illustrated embodiment of  FIG. 15 , the shank  40   b  extends through the blade  34 . Aqueous flows from the anterior chamber  20  into the lumen  42   b  through an inlet port  54   b  (as generally indicated by arrow  58   b ). Aqueous then flows through the output channels  45   b  and out of respective outlet ports  56   b  and into Schlemm&#39;s canal  22  (as generally indicated by arrows  60   b ). The outlet channels  45   b  extend radially outwards in generally opposed directions and the outlet ports  56   b  are configured to face in the general direction of the stent longitudinal axis  36  so that they open into Schlemm&#39;s canal  22  and are in proper orientation to allow aqueous outflow into Schlemm&#39;s canal  22  for lowering and/or balancing the intraocular pressure (IOP). As indicated above, fiducial marks or indicia and/or predetermined shapes of the snorkel seat  38  allow for proper orientation of the blade  34  and also the output channels  45   b  and respective ports  56   b  within Schlemm&#39;s canal. 
     In the illustrated embodiment of  FIG. 15 , two outflow channels  45   b  are provided. In another embodiment, only one outflow channel  45   b  is provided. In yet another embodiment, more than two outflow channels  45   b  are provided. In modified embodiments, the lumen  42   b  may extend all the way through to the blade  34  and provide an outlet port as discussed above with reference to the embodiment of  FIGS. 3-9 . 
       FIGS. 16-20  show different views of a self-trephining glaucoma stent device  30   c  having features and advantages in accordance with one embodiment. The stent  30   c  is generally similar to the stent  30  of  FIGS. 3-9  except that it has a modified blade configuration. The stent  30   c  comprises a blade  34   c  which is a generally curved elongated sheet- or plate-like structure with an upper curved surface  62   c  and a lower curved surface  64   c  which defines a trough or open face channel  66   c . The perimeter of the blade  34   c  is generally defined by a curved proximal edge  68   c  proximate to the snorkel  32 , a curved distal edge  70   c  spaced from the proximal edge  68   c  by a pair of generally straight lateral edges  72   c ,  74   c  which are generally parallel to one another and have about the same length. 
     In the illustrated embodiment of  FIGS. 16-20 , the blade  34   c  comprises a cutting tip  78   c . The cutting tip  78   c  preferably includes cutting edges formed on selected portions of the distal edge  70   c  and adjacent portions of the lateral edges  72   c ,  74   c  for cutting through the trabecular meshwork for placement of the snorkel  32 . The cutting edges are sharp edges of beveled or tapered surfaces as discussed above in reference to  FIG. 9 . The embodiment of  FIGS. 16-20  may be efficaciously modified to incorporate the snorkel configuration of the embodiments of  FIGS. 14 and 15 . 
       FIGS. 21-25  show different views of a self-trephining glaucoma stent device  30   d  having features and advantages in accordance with one embodiment. The stent  30   d  is generally similar to the stent  30  of  FIGS. 3-9  except that it has a modified blade configuration. The stent  30   d  comprises a blade  34   d  which is a generally curved elongated sheet- or plate-like structure with an upper curved surface  62   d  and a lower curved surface  64   d  which defines a trough or open face channel  66   d . The perimeter of the blade  34   d  is generally defined by a curved proximal edge  68   d  proximate to the snorkel  32 , a pair of inwardly converging curved distal edges  70   d ′,  70   d ″ spaced from the proximal edge  68   d  by a pair of generally straight respective lateral edges  72   d ,  74   d  which are generally parallel to one another and have about the same length. The distal edges  70   d ′,  70   d ″ intersect at a distal-most point  76   d  of the blade  34   d  proximate a blade cutting tip  78   d.    
     In the illustrated embodiment of  FIGS. 21-25 , the cutting tip  78   d  preferably includes cutting edges formed on the distal edges  70   d ′,  70   d ″ and extending from the distal-most point  76   d  of the blade  34   d . In one embodiment, the cutting edges extend along only a portion of respective distal edges  70   d ′,  70   d ″. In another embodiment, the cutting edges extend along substantially the entire length of respective distal edges  70   d ′,  70   d ″. In yet another embodiment, at least portions of the lateral edges  72   d ,  74   d  proximate to respective distal edges  70   d ′,  70   d ″ have cutting edges. In a further embodiment, the tip  78   d  proximate to the distal-most end  76   d  is curved slightly inwards, as indicated generally by the arrow  88   d  in  FIG. 21  and arrow  88   d  (pointed perpendicular and into the plane of the paper) in  FIG. 22 , relative to the adjacent curvature of the blade  34   d.    
     In the embodiment of  FIGS. 21-25 , the cutting edges are sharp edges of beveled or tapered surfaces as discussed above in reference to  FIG. 9 . The embodiment of  FIGS. 21-25  may be efficaciously modified to incorporate the snorkel configuration of the embodiments of  FIGS. 14 and 15 . 
       FIGS. 26-28  show different views of a self-trephining glaucoma stent device  30   e  having features and advantages in accordance with one embodiment. The stent device  30   e  generally comprises a snorkel  32   e  mechanically connected to or in mechanical communication with a blade or cutting tip  34   e . The snorkel  32   e  has a seat, head or cap portion  38   e  mechanically connected to or in mechanical communication with a shank  40   e , as discussed above. The shank  40   e  has a distal end or base  47   e . The snorkel  32   e  further has a lumen  42   e  which bifurcates into a pair of outlet channels  45   e , as discussed above in connection with  FIGS. 14 and 15 . Other lumen and inlet and outlet port configurations as taught or suggested herein may also be efficaciously used, as needed or desired. 
     In the illustrated embodiment of  FIGS. 26-28 , the blade  34   e  extends downwardly and outwardly from the shank distal end  47   e . The blade  34   e  is angled relative to a generally longitudinal axis  43   e  of the snorkel  32   e , as best seen in  FIGS. 27 and 28 . The blade  34   e  has a distal-most point  76   e . The blade or cutting tip  34   e  has a pair of side edges  70   e ′,  70   e ″, including cutting edges, terminating at the distal-most point  76   e , as best seen in  FIG. 26 . In one embodiment, the cutting edges are sharp edges of beveled or tapered surfaces as discussed above in reference to  FIG. 9 . 
     Referring to  FIGS. 26-28 , in one embodiment, the blade  34   e  includes cutting edges formed on the edges  70   e ′,  70   e ″ and extending from the distal-most point  76   e  of the blade  34   d . In one embodiment, the cutting edges extend along only a portion of respective distal edges  70   e ′,  70   e ″. In another embodiment, the cutting edges extend along substantially the entire length of respective distal edges  70   e ′,  70   e ″. In yet another embodiment, the blade or cutting tip  34   e  comprises a bent tip of needle, for example, a 30 gauge needle. 
     In general, any of the blade configurations disclosed herein may be used in conjunction with any of the snorkel configurations disclosed herein or incorporated by reference herein to provide a self-trephining glaucoma stent device for making an incision in the trabecular meshwork for receiving the corresponding snorkel to provide a pathway for aqueous outflow from the eye anterior chamber to Schlemm&#39;s canal, thereby effectively lowering and/or balancing the intraocular pressure (IOP). The self-trephining ability of the device, advantageously, allows for a “one-step” procedure in which the incision and placement of the snorkel are accomplished by a single device and operation. In any of the embodiments, fiducial markings or indicia, and/or preselected configuration of the snorkel seat, and/or positioning of the stent device in a preloaded applicator may be used for proper orientation and alignment of the device during implantation. 
     Delivery Apparatus 
     In many cases, a surgeon works from a temporal incision when performing cataract or goniometry surgery.  FIG. 29  illustrates a temporal implant procedure, wherein a delivery apparatus or “applicator”  100  having a curved tip  102  is used to deliver a stent  30  to a temporal side  27  of the eye  10 . An incision  28  is made in the cornea  10 , as discussed above. The apparatus  100  is then used to introduce the stent  30  through the incision  28  and implant it within the eye  10 . 
     Still referring in particular to  FIG. 29 , in one embodiment, a similarly curved instrument would be used to make the incision through the trabecular meshwork  21 . In other embodiments, a self-trephining stent device  30  may be used to make this incision through the trabecular meshwork  21 , as discussed above. The temporal implantation procedure illustrated in  FIG. 29  may be employed with the any of the various stent embodiments taught or suggested herein. 
       FIG. 30  illustrates one embodiment of an apparatus comprising an articulating stent applicator or retrieval device  100   a . In this embodiment, a proximal arm  106  is attached to a distal arm  108  at a joint  112 . This joint  112  is movable such that an angle formed between the proximal arm  106  and the distal arm  108  can change. One or more claws  114  can extend from the distal arm  108 , in the case of a stent retrieval device. Similarly, this articulation mechanism may be used for the trabecular stent applicator, and thus the articulating applicator or retrieval device  100   a  may be either an applicator for the trabecular stent, a retrieval device, or both, in various embodiments. The embodiment of  FIG. 30  may be employed with the any of the various stent embodiments taught or suggested herein. 
       FIG. 31  shows another illustrative method for placing any of the various stent embodiments taught or suggested herein at the implant site within the eye  10 . A delivery apparatus  100   b  generally comprises a syringe portion  116  and a cannula portion  118 . The distal section of the cannula  118  has at least one irrigating hole  120  and a distal space  122  for holding the stent device  30 . The proximal end  124  of the lumen of the distal space  122  is sealed from the remaining lumen of the cannula portion  118 . The delivery apparatus of  FIG. 30  may be employed with the any of the various stent embodiments taught or suggested herein. 
     In one aspect of the invention, a delivery apparatus (or “applicator”) is used for placing a trabecular stent through a trabecular meshwork of an eye. Certain embodiments of such a delivery apparatus are disclosed in copending U.S. application Ser. No. 10/101,548 (Inventors: Gregory T. Smedley, Irvine, Calif., Morteza Gharib, Pasadena, Calif., Hosheng Tu, Newport Beach, Calif.), filed Mar. 18, 2002, entitled APPLICATOR AND METHODS FOR PLACING A TRABECULAR SHUNT FOR GLAUCOMA TREATMENT, and U.S. Provisional Application No. 60/276,609, filed Mar. 16, 2001, entitled APPLICATOR AND METHODS FOR PLACING A TRABECULAR SHUNT FOR GLAUCOMA TREATMENT, the entire contents of each one of which are hereby incorporated by reference herein. 
     The stent has an inlet section and an outlet section. The delivery apparatus includes a handpiece, an elongate tip, a holder and an actuator. The handpiece has a distal end and a proximal end. The elongate tip is connected to the distal end of the handpiece. The elongate tip has a distal portion and is configured to be placed through a corneal incision and into an anterior chamber of the eye. The holder is attached to the distal portion of the elongate tip. The holder is configured to hold and release the inlet section of the trabecular stent. The actuator is on the handpiece and actuates the holder to release the inlet section of the trabecular stent from the holder. When the trabecular stent is deployed from the delivery apparatus into the eye, the outlet section is positioned in substantially opposite directions inside Schlemm&#39;s canal. In one embodiment, a deployment mechanism within the delivery apparatus includes a push-pull type plunger. 
     In some embodiments, the holder comprises a clamp. In some embodiments, the apparatus further comprises a spring within the handpiece that is configured to be loaded when the stent is being held by the holder, the spring being at least partially unloaded upon actuating the actuator, allowing for release of the stent from the holder. 
     In various embodiments, the clamp comprises a plurality of claws configured to exert a clamping force onto the inlet section of the stent. The holder may also comprise a plurality of flanges. 
     In some embodiments, the distal portion of the elongate tip is made of a flexible material. This can be a flexible wire. The distal portion can have a deflection range, preferably of about 45 degrees from the long axis of the handpiece. 
     The delivery apparatus can further comprise an irrigation port in the elongate tip. 
     Some aspects include a method of placing a trabecular stent through a trabecular meshwork of an eye, the stent having an inlet section and an outlet section, including advancing a delivery apparatus holding the trabecular stent through an anterior chamber of the eye and into the trabecular meshwork, placing part of the stent through the trabecular meshwork and into a Schlemm&#39;s canal of the eye; and releasing the stent from the delivery apparatus. 
     In various embodiments, the method includes using a delivery apparatus that comprises a handpiece having a distal end and a proximal end; an elongate tip connected to the distal end of the handpiece, the elongate tip having a distal portion and being configured to be placed through a corneal incision and into an anterior chamber of the eye; a holder attached to the distal portion of the elongate tip, the holder configured to hold and release the inlet section of the trabecular stent; and an actuator on the handpiece that actuates the holder to release the inlet section of the trabecular stent from the holder. 
     In one aspect, the trabecular stent is removably attached to a delivery apparatus (also known as “applicator”). When the trabecular stent is deployed from the delivery apparatus into the eye, the outlet section is positioned in substantially opposite directions inside Schlemm&#39;s canal. In one embodiment, a deployment mechanism within the delivery apparatus includes a push-pull type plunger. In some embodiments, the delivery applicator may be a guidewire, an expandable basket, an inflatable balloon, or the like. 
     Other Embodiments 
     Screw/Barb Anchored Stent: 
       FIGS. 32 and 33  illustrate a glaucoma stent device  30   f  having features and advantages in accordance with one embodiment. This embodiment of the trabecular stent  30   f  includes a barbed or threaded screw-like extension or pin  126  with barbs  128  for anchoring. The barbed pin  126  extends from a distal or base portion  130  of the stent  30   f.    
     In use, the stent  30   f  ( FIG. 32 ) is advanced through the trabecular meshwork  21  and across Schlemm&#39;s canal  22 . The barbed (or threaded) extension  126  penetrates into the back wall  92  of Schlemm&#39;s canal  22  up to the shoulder or base  130  that then rests on the back wall  92  of the canal  22 . The combination of a shoulder  130  and a barbed pin  126  of a particular length limits the penetration depth of the barbed pin  126  to a predetermined or preselected distance. In one embodiment, the length of the pin  126  is about 0.5 mm or less. Advantageously, this barbed configuration provides a secure anchoring of the stent  30   f . As discussed above, correct orientation of the stent  30   f  is ensured by appropriate fiducial marks, indicia or the like and by positioning of the stent in a preloaded applicator. 
     Referring to  FIG. 32 , the aqueous flows from the anterior chamber  20 , through the lumen  42   f , then out through two side-ports  56   f  to be directed in both directions along Schlemm&#39;s canal  22 . Alternatively, flow could be directed in only one direction through a single side-port  56   f . In other embodiments, more then two outlet ports  56   f , for example, six to eight ports (like a pin wheel configuration), may be efficaciously used, as needed or desired. 
     Still referring to  FIG. 32 , in one embodiment, the stent  30   f  is inserted through a previously made incision in the trabecular meshwork  21 . In other embodiments, the stent  30   f  may be combined with any of the blade configurations taught or suggested herein to provide self-trephining capability. In these cases, the incision through the trabecular meshwork  21  is made by the self-trephining stent device which has a blade at its base or proximate to the base. 
     Deeply Threaded Stent: 
       FIG. 34  illustrates a glaucoma stent device  30   g  having features and advantages in accordance with one embodiment. The stent  30   g  has a head or seat  38   g  and a shank or main body portion  40   g  with a base or distal end  132 . This embodiment of the trabecular stent  30   g  includes a deep thread  134  (with threads  136 ) on the main body  40   g  of the stent  30   g  below the head  38   g . The threads may or may not extend all the way to the base  132 . 
     In use, the stent  30   g  ( FIG. 34 ) is advanced through the meshwork  21  through a rotating motion, as with a conventional screw. Advantageously, the deep threads  136  provide retention and stabilization of the stent  30   g  in the trabecular meshwork  21 . 
     Referring to  FIG. 34 , the aqueous flows from the anterior chamber  20 , through the lumen  42   g , then out through two side-ports  56   g  to be directed in both directions along Schlemm&#39;s canal  22 . Alternatively, flow could be directed in only one direction through a single side-port  56   g . In other embodiments, more then two outlet ports  56   g  may be efficaciously used, as needed or desired. 
     One suitable applicator or delivery apparatus for this stent  30   g  ( FIG. 34 ) includes a preset rotation, for example, via a wound torsion spring or the like. The rotation is initiated by a release trigger on the applicator. A final twist of the applicator by the surgeon and observation of suitable fiducial marks, indicia or the like ensure proper alignment of the side ports  56   g  with Schlemm&#39;s canal  22 . 
     Referring to  FIG. 34 , in one embodiment, the stent  30   g  is inserted through a previously made incision in the trabecular meshwork  21 . In other embodiments, the stent  30   g  may be combined with any of the blade configurations taught or suggested herein to provide self-trephining capability. In these cases, the incision through the trabecular meshwork  21  is made by the self-trephining stent device which has a blade at its base or proximate to the base. 
     Rivet Style Stent: 
       FIG. 35  illustrates a glaucoma stent device  30   h  having features and advantages in accordance with one embodiment. The stent has a base or distal end  138 . This embodiment of the trabecular stent  30   h  has a pair of flexible ribs  140 . In the unused state, the ribs are initially generally straight (that is, extend in the general direction of arrow  142 ). 
     Referring to  FIG. 35 , upon insertion of the stent  30   h  through the trabecular meshwork  21 , the ends  144  of respective ribs  140  of the stent  30   h  come to rest on the back wall  92  of Schlemm&#39;s canal  22 . Further advancement of the stent  30   h  causes the ribs  140  to deform to the bent shape as shown in the drawing of  FIG. 35 . The ribs  140  are designed to first buckle near the base  138  of the stent  30   h . Then the buckling point moves up the ribs  140  as the shank part  40   h  of the stent  30   h  is further advanced through the trabecular meshwork  21 . 
     The lumen  42   h  ( FIG. 35 ) in the stent  30   h  is a simple straight hole. The aqueous flows from the anterior chamber  20 , through the lumen  42   h , then out around the ribs  140  to the collector channels further along Schlemm&#39;s canal  22  in either direction. 
     Referring to  FIG. 35 , in one embodiment, the stent  30   h  is inserted through a previously made incision in the trabecular meshwork  21 . In other embodiments, the stent  30   h  may be combined with any of the blade configurations taught or suggested herein to provide self-trephining capability. In these cases, the incision through the trabecular meshwork  21  is made by the self-trephining stent device which has a blade at its base or proximate to the base. 
     Grommet Style Stent: 
       FIG. 36  illustrates a glaucoma stent device  30   i  having features and advantages in accordance with one embodiment. This embodiment of the trabecular stent  30   i  includes a head or seat  38   i , a tapered base portion  146  and an intermediate narrower waist portion or shank  40   i.    
     In use, the stent  30   i  ( FIG. 36 ) is advanced through the trabecular meshwork  21  and the base  146  is pushed into Schlemm&#39;s canal  22 . The stent  30   i  is pushed slightly further, if necessary, until the meshwork  21  stretched by the tapered base  146  relaxes back and then contracts to engage the smaller diameter portion waist  40   i  of the stent  30   i . Advantageously, the combination of the larger diameter head or seat  38   i  and base  146  of the stent  30   i  constrains undesirable stent movement. As discussed above, correct orientation of the stent  30   i  is ensured by appropriate fiducial marks, indicia or the like and by positioning of the stent in a preloaded applicator. 
     Referring to  FIG. 36 , the aqueous flows from the anterior chamber  20 , through the lumen  42   i , then out through two side-ports  56   i  to be directed in both directions along Schlemm&#39;s canal  22 . Alternatively, flow could be directed in only one direction through a single side-port  56   i . In other embodiments, more then two outlet ports  56   i  may be efficaciously used, as needed or desired. 
     Still referring to  FIG. 36 , in one embodiment, the stent  30   i  is inserted through a previously made incision in the trabecular meshwork  21 . In other embodiments, the stent  30   i  may be combined with any of the blade configurations taught or suggested herein to provide self-trephining capability. In these cases, the incision through the trabecular meshwork  21  is made by the self-trephining stent device which has a blade at its base or proximate to the base. 
     Biointeractive Stent: 
       FIG. 37  illustrates a glaucoma stent device  30   j  having features and advantages in accordance with one embodiment. This embodiment of the trabecular stent  30   j  utilizes a region of biointeractive material  148  that provides a site for the trabecular meshwork  21  to firmly grip the stent  30   j  by ingrowth of the tissue into the biointeractive material  148 . As shown in  FIG. 37 , preferably the biointeractive layer  148  is applied to those surfaces of the stent  30   j  which would abut against or come in contact with the trabecular meshwork  21 . 
     In one embodiment, the biointeractive layer  148  ( FIG. 37 ) may be a region of enhanced porosity with a growth promoting chemical. In one embodiment, a type of bio-glue  150  that dissolves over time is used to hold the stent secure during the time between insertion and sufficient ingrowth for stabilization. As discussed above, correct orientation of the stent  30   j  is ensured by appropriate fiducial marks, indicia or the like and by positioning of the stent in a preloaded applicator. 
     Referring to  FIG. 37 , the aqueous flows from the anterior chamber  20 , through the lumen  42   j , then out through two side-ports  56   j  to be directed in both directions along Schlemm&#39;s canal  22 . Alternatively, flow could be directed in only one direction through a single side-port  56   j . In other embodiments, more then two outlet ports  56   j  may be efficaciously used, as needed or desired. 
     Still referring to  FIG. 37 , in one embodiment, the stent  30   j  is inserted through a previously made incision in the trabecular meshwork  21 . In other embodiments, the stent  30   j  may be combined with any of the blade configurations taught or suggested herein to provide self-trephining capability. In these cases, the incision through the trabecular meshwork  21  is made by the self-trephining stent device which has a blade at its base or proximate to the base. 
     Glued or Welded Stent: 
       FIG. 38  illustrates a glaucoma stent device  30   k  having features and advantages in accordance with one embodiment. This embodiment of the trabecular stent  30   k  is secured in place by using a permanent (non-dissolving) bio-glue  152  or a “welding” process (e.g. heat) to form a weld  152 . The stent  30   k  has a head or seat  38   k  and a lower surface  46   k.    
     The stent  30   k  is advanced through the trabecular meshwork  21  until the head or seat  38   k  comes to rest on the trabecular meshwork  21 , that is, the head lower surface  46   k  abuts against the trabecular meshwork  21 , and the glue or weld  152  is applied or formed therebetween, as shown in  FIG. 38 . As discussed above, correct orientation of the stent  30   k  is ensured by appropriate fiducial marks, indicia or the like and by positioning of the stent in a preloaded applicator. 
     Referring to  FIG. 38 , the aqueous flows from the anterior chamber  20 , through the lumen  42   k , then out through two side-ports  56   k  to be directed in both directions along Schlemm&#39;s canal  22 . Alternatively, flow could be directed in only one direction through a single side-port  56   k . In other embodiments, more then two outlet ports  56   k  may be efficaciously used, as needed or desired. 
     Still referring to  FIG. 38 , in one embodiment, the stent  30   k  is inserted through a previously made incision in the trabecular meshwork  21 . In other embodiments, the stent  30   k  may be combined with any of the blade configurations taught or suggested herein to provide self-trephining capability. In these cases, the incision through the trabecular meshwork  21  is made by the self-trephining stent device which has a blade at its base or proximate to the base. 
     Hydrophilic Latching Stent: 
       FIG. 39  illustrates a glaucoma stent device  30   m  having features and advantages in accordance with one embodiment. This embodiment of the trabecular stent  30   m  is fabricated from a hydrophilic material that expands with absorption of water. Desirably, this would enable the device  30   m  to be inserted through a smaller incision in the trabecular meshwork  21 . The subsequent expansion (illustrated by the smaller arrows  154 ) of the stent  30   m  would advantageously enable it to latch in place in the trabecular meshwork  21 . As discussed above, correct orientation of the stent  30   m  is ensured by appropriate fiducial marks, indicia or the like and by positioning of the stent in a preloaded applicator. 
     Referring to  FIG. 39 , the aqueous flows from the anterior chamber  20 , through the lumen  42   m , then out through two side-ports  56   m  to be directed in both directions along Schlemm&#39;s canal  22 . Alternatively, flow could be directed in only one direction through a single side-port  56   m . In other embodiments, more then two outlet ports  56   m  may be efficaciously used, as needed or desired. 
     Still referring to  FIG. 39 , in one embodiment, the stent  30   m  is inserted through a previously made incision in the trabecular meshwork  21 . In other embodiments, the stent  30   m  may be combined with any of the blade configurations taught or suggested herein to provide self-trephining capability. In these cases, the incision through the trabecular meshwork  21  is made by the self-trephining stent device which has a blade at its base or proximate to the base. 
     Photodynamic Stent: 
       FIG. 40  illustrates a glaucoma stent device  30   n  having features and advantages in accordance with one embodiment. This embodiment of the trabecular stent  30   n  is fabricated from a photodynamic material that expands on exposure to light. 
     It is commonly known that there is a diurnal variation in the aqueous humor production by the eye—it is higher during the day than it is at night. The lumen  42   n  of the stent  30   n  responds to light entering the cornea during the day by expanding and allowing higher flow of aqueous through the lumen  42   n  and into Schlemm&#39;s canal  22 . This expansion is generally indicated by the smaller arrows  156  ( FIG. 40 ) which show the lumen  42   n  (and ports) expanding or opening in response to light stimulus. (The light or radiation energy E is generally given by E=hν, where h is Planck&#39;s constant and ν is the frequency of the light provided.) At night, in darkness, the lumen diameter decreases and reduces the flow allowed through the lumen  42   n . In one embodiment, an excitation wavelength that is different from that commonly encountered is provided on an as-needed basis to provide higher flow of aqueous to Schlemm&#39;s canal  22 . 
     This photodynamic implementation is shown in  FIG. 40  for the self-latching style of stent  30   n , but can be efficaciously used with any of the other stent embodiments, as needed or desired. As discussed above, correct orientation of the stent  30   n  is ensured by appropriate fiducial marks, indicia or the like and by positioning of the stent in a preloaded applicator. 
     Referring to  FIG. 40 , the aqueous flows from the anterior chamber  20 , through the lumen  42   n , then out through two side-ports  56   n  to be directed in both directions along Schlemm&#39;s canal  22 . Alternatively, flow could be directed in only one direction through a single side-port  56   n . In other embodiments, more then two outlet ports  56   n  may be efficaciously used, as needed or desired. 
     Still referring to  FIG. 40 , in one embodiment, the stent  30   n  is inserted through a previously made incision in the trabecular meshwork  21 . In other embodiments, the stent  30   n  may be combined with any of the blade configurations taught or suggested herein to provide self-trephining capability. In these cases, the incision through the trabecular meshwork  21  is made by the self-trephining stent device which has a blade at its base or proximate to the base. 
     Collector Channel Alignment Stent: 
       FIG. 41  illustrates a glaucoma stent device  30   p  having features and advantages in accordance with one embodiment. This figure depicts an embodiment of a stent  30   p  that directs aqueous from the anterior chamber  20  directly into a collector channel  29  which empties into aqueous veins. The stent  30   p  has a base or distal end  160 . 
     In the illustrated embodiment of  FIG. 41 , a removable alignment pin  158  is utilized to align the stent lumen  42   p  with the collector channel  29 . In use, the pin  158  extends through the stent lumen  42   p  and protrudes through the base  160  and extends into the collector channel  29  to center and/or align the stent  30   p  over the collector channel  29 . The stent  30   p  is then pressed firmly against the back wall  92  of Schlemm&#39;s canal  22 . A permanent bio-glue  162  is used between the stent base and the back wall  92  of Schlemm&#39;s canal  22  to seat and securely hold the stent  30   p  in place. Once positioned, the pin  158  is withdrawn from the lumen  42   p  to allow the aqueous to flow directly from the anterior chamber  20  into the collector duct  29 . The collector ducts are nominally 20 to 100 micrometers (μm) in diameter and are visualized with a suitable microscopy method (such as ultrasound biomicroscopy (UBM)) or laser imaging to provide guidance for placement of the stent  30   p.    
     Referring to  FIG. 41 , in one embodiment, the stent  30   p  is inserted through a previously made incision in the trabecular meshwork  21 . In other embodiments, the stent  30   p  may be combined with any of the blade configurations taught or suggested herein to provide self-trephining capability. In these cases, the incision through the trabecular meshwork  21  is made by the self-trephining stent device which has a blade at its base or proximate to the base. 
     Barbed Stent (Anterior Chamber to Collector Channel): 
       FIG. 42  illustrates a glaucoma stent device  30   q  having features and advantages in accordance with one embodiment. This figure depicts an embodiment of a stent  30   q  that directs aqueous from the anterior chamber  20  directly into a collector channel  29  which empties into aqueous veins. The stent  30   q  has a base or distal end  166  and the channel  29  has wall(s)  164 . 
     In the illustrated embodiment of  FIG. 42 , a barbed, small-diameter extension or pin  168  on the stent base  166  is guided into the collector channel  29  and anchors on the wall(s)  164  of the channel  29 . The pin  168  has barbs  170  which advantageously provide anchoring of the stent  30   q . The collector ducts  29  are nominally 20 to 100 micrometers (μm) in diameter and are visualized with a suitable microscopy method (such as ultrasound biomicroscopy (UBM)) or laser imaging to provide guidance for placement of the stent. 
     Referring to  FIG. 42 , in one embodiment, the stent  30   q  is inserted through a previously made incision in the trabecular meshwork  21 . In other embodiments, the stent  30   q  may be combined with any of the blade configurations taught or suggested herein to provide self-trephining capability. In these cases, the incision through the trabecular meshwork  21  is made by the self-trephining stent device which has a blade at its base or proximate to the base. 
     Valved Tube Stent (Anterior Chamber to Choroid): 
       FIG. 43  illustrates a valved tube stent device  30   r  having features and advantages in accordance with one embodiment. This is an embodiment of a stent  30   r  that provides a channel for flow between the anterior chamber  20  and the highly vascular choroid  17 . Clinically, the choroid  17  can be at pressures lower than those desired for the eye  10 . Therefore, this stent  30   r  includes a valve with an opening pressure equal to the desired pressure difference between the choroid  17  and the anterior chamber  10  or a constriction that provide the desired pressure drop. 
     Osmotic Membrane (Anterior Chamber to Choroid): 
       FIG. 44  illustrates an osmotic membrane device  30   s  having features and advantages in accordance with one embodiment. This embodiment provides a channel for flow between the anterior chamber  20  and the highly vascular choroid  17 . The osmotic membrane  30   s  is used to replace a portion of the endothelial layer of the choroid  17 . Since the choroid  17  is highly vascular with blood vessels, the concentration of water on the choroid side is lower than in the anterior chamber  20  of the eye  10 . Therefore, the osmotic gradient drives water from the anterior chamber  20  into the choroid  17 . 
     Clinically, the choroid  17  ( FIG. 44 ) can be at pressures lower than those desired for the eye  10 . Therefore, desirably, both osmotic pressure and the physical pressure gradient are in favor of flow into the choroid  17 . Flow control is provided by proper sizing of the area of the membrane, —the larger the membrane area is the larger the flow rate will be. This advantageously enables tailoring to tune the flow to the desired physiological rates. 
     Ab Externo Insertion of Stent Via Small Puncture: 
       FIG. 45  illustrates the implantation of a stent  30   t  using an ab externo procedure having features and advantages in accordance with one embodiment. In the ab externo procedure of  FIG. 45 , the stent  30   t  is inserted into Schlemm&#39;s canal  21  with the aid of an applicator or delivery apparatus  100   c  that creates a small puncture into the eye  10  from outside. 
     Referring to  FIG. 45 , the stent  30   t  is housed in the applicator  100   c , and pushed out of the applicator  100   c  once the applicator tip is in position within the trabecular meshwork  21 . Since the tissue surrounding the trabecular meshwork  21  is optically opaque, an imaging technique, such as ultrasound biomicroscopy (UBM) or a laser imaging technique, is utilized. The imaging provides guidance for the insertion of the applicator tip and the deployment of the stent  30   t . This technique can be used with a large variety of stent embodiments with slight modifications since the trabecular meshwork  21  is punctured from the scleral side rather than the anterior chamber side in the ab externo insertion. 
       FIG. 46  a glaucoma stent device  30   u  having features and advantages in accordance with a modified embodiment. This grommet-style stent  30   u  for ab externo insertion is a modification of the embodiment of  FIG. 36 . In the embodiment of  FIG. 46 , the upper part or head  38   u  is tapered while the lower part or base  172  is flat, as opposed to the embodiment of  FIG. 36 . The stent  30   u  is inserted from the outside of the eye  10  through a puncture in the sclera. Many of the other embodiments of stents taught or suggested herein can be modified for similar implantation. 
     This ultra microscopic device  30   u  ( FIG. 46 ) can be used with (1) a targeting Lasik-type laser, or with (2) contact on eyes or with (3) combined ultrasound microscope or (4) other device inserter handpiece. 
     Targeted Drug Delivery to the Trabecular Meshwork: 
       FIG. 47  illustrates a targeted drug delivery implant  30   v  having features and advantages in accordance with one embodiment. This drawing is a depiction of a targeted drug delivery concept. The slow release implant  30   v  is implanted within the trabecular meshwork  21 . 
     A drug that is designed to target the trabecular meshwork  21  to increase its porosity, or improve the active transport across the endothelial layer of Schlemm&#39;s canal  22  can be stored in this small implant  30   v  ( FIG. 47 ). Advantageously, slow release of the drug promotes the desired physiology at minimal dosage levels since the drug is released into the very structure that it is designed to modify. 
     While the components and techniques of the invention have been described with a certain degree of particularity, it is manifest that many changes may be made in the specific designs, constructions and methodology herein above described without departing from the spirit and scope of this disclosure. It should be understood that the invention is not limited to the embodiments set forth herein for purposes of exemplification, but is to be defined only by a fair reading of the appended claims, including the full range of equivalency to which each element thereof is entitled.