Glaucoma implant with a temporary flow restricting seal

An implant for use in the treatment of glaucoma is disclosed wherein the implant comprises an elastomeric plate having a non-valved elastomeric drainage tube attached thereto. The plate is curved so as to conform to the spherical anatomy of the eyeball. An annular sloped wall extends from the plate and surrounds the opening of the drainage tube into the plate. The plate is inserted beneath Tenon's capsule and sutured to the sclera utilizing temporary and non-dissolving permanent sutures. The annular wall provides a temporary sealing surface against the sclera. The drainage tube is tunnelled through the sclera and cornea and inserted into the anterior chamber, thus providing fluid communication between the anterior chamber and the elastomeric plate. The annular wall around the tube forms a temporary seal which restricts the drainage of aqueous fluid until formation of the bleb is completed. After bleb formation occurs, the temporary sutures around the wall are removed or dissolve. Once the temporary sutures are gone, the portion of the plate that is not stitched to the sclera floats within the bleb and breaks the seal between the implant and the sclera. Once the seal is broken, unrestricted flow between the anterior chamber and bleb is maintained.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The invention relates to ocular implants, and, in particular, to an implant 
used in the treatment of glaucoma. 
2. Background 
Intraocular pressure in the eye is maintained by the formation and drainage 
of aqueous, a clear, colorless fluid that fills the anterior and posterior 
chambers of the eye. Aqueous normally flows from the anterior chamber of 
the eye out through an aqueous outflow channel at a rate of 2 to 5 
microliters per minute. 
Glaucoma is a progressive disease of the eye characterized by a gradual 
increase of intraocular pressure. This increase in pressure is most 
commonly caused by stenosis or blockage of the aqueous outflow channel, 
resulting in excessive buildup of aqueous fluid in the eyeball. Other 
causes include increase in venous pressure outside the eye which is 
reflected back through the aqueous drainage channels and increased 
production of aqueous. In a "normal" eye, intraocular pressure ranges from 
8 to 21 mm mercury. In an eye with glaucoma, this pressure can range 
between the so called normal pressures and pressures up to as much as 50 
mm mercury. This increase in intraocular pressure produces gradual and 
permanent loss of vision in the afflicted eye. 
Existing corrective methods for the treatment of glaucoma include drugs, 
surgery, and implants. Pharmacological treatment is prohibitively 
expensive to a large majority of glaucoma patients. In addition, many 
people afflicted with the disease live in remote or undeveloped retirement 
areas where the drugs are not readily accessible. The drugs used in the 
treatment, in particular steroids, often have undesirable side effects and 
many of the long-term effects resulting from prolonged use are not yet 
known. 
Surgical procedures have been developed in an effort to treat victims of 
glaucoma. An iridectomy, removal of a portion of the iris, is often used 
in angle-closure glaucoma wherein there is an occlusion of the trabecular 
meshwork by iris contact. Removal of a piece of the iris then gives the 
aqueous free passage from the posterior to the anterior chambers in the 
eye. A trabeculotomy, opening the inner wall of Schlemm's canal, is often 
performed in cases of developmental or juvenile glaucoma so as to increase 
the outflow of the aqueous, thereby decreasing intraocular pressure. In 
adults, a trabeculotomy shunts fluid through a trap-door flap in the eye 
that performs a valve-like function for the first few weeks after surgery. 
While often successful, these surgical techniques possess inherent risks 
associated with invasive surgery on an already afflicted eye. Furthermore, 
the tissue of the eye can scar over this small area and the eye reverts to 
the pre-operative condition, thereby necessitating the need for further 
treatment. 
Ocular implants are often used in long-term glaucoma treatment. One such 
implant is disclosed in U.S. Pat. No. 4,457,757 entitled "Device for 
Draining Aqueous Humor" and commercially available as the Molteno.TM. 
Seton Implant. The implant comprises a drainage tube connected to one or 
more rigid plate reservoirs. The reservoir plates conform to the curvature 
of the eye. A reservoir plate is placed under Tenon's capsule and sutured 
to the sclera. 
The drainage tube is implanted into the anterior chamber through a scleral 
flap. A second plate can be passed under the superior rectus muscle and 
sutured to the sclera. At this point, the body will form scar tissue 
around these plates. Increased pressure causes the tissues above the 
plates to lift and form a bleb into which aqueous flows from the anterior 
chamber drains via the drainage tube. This type of implant is 
disadvantageous as the plates are formed of a rigid plastic which makes 
insertion beneath the eye tissue difficult and time-consuming. 
UK Patent Application 2,160,778 entitled "Aqueous humor drainage device" 
discloses a similar type of implant device comprising a drainage tube and 
a drainage body. The tube is fixed to and opens directly onto a surface of 
the body. The device is sutured to the sclera of the eye and the tube 
positioned within the anterior chamber to provide outflow for the aqueous 
contained therein. The device further includes a pressure gradient 
limiting valve formed as a slit in the tube. However, when the device is 
implanted in the eye and is surrounded by aqueous humor, an extremely 
small flow rate of aqueous humor will pass through the slit, thus the slit 
in the tube functions not as a valve but as a flow restrictor. This type 
of device does not allow patent, i.e., open or two-way, flow through the 
drainage tube, and prevents retrograde aqueous flow into the anterior 
chamber. This device is considered a valved glaucoma implant because it 
has a permanent structure in the flow path obstructing the flow of aqueous 
from the anterior chamber. A non-valved device has a patent uninterrupted 
flow of aqueous to and from the anterior chamber, i.e., the implant has no 
permanent structure in the fluid flow path which obstructs the flow of the 
aqueous. 
During the first few days after surgery and before scar tissue forms a bleb 
around the glaucoma implant device, it is possible for too much fluid to 
flow from the eye and create an extremely low to zero pressure in the eye. 
This low pressure could cause the eye to collapse and cause considerable 
and often permanent damage to the eye. It is desirable to provide a 
sealing mechanism that would prevent this pressure drop during the initial 
stages of the bleb formation and would enable a greater pressure release 
once the bleb has formed. Actual experience has shown that it is often 
necessary to apply a "purse-string" suture around the drainage tube which 
occludes drainage flow until the bleb has formed. Generally, the scar 
formation requires up to 8 weeks. After the scar is formed, the suture 
dissolves, but occasionally a second surgical procedure is necessary to 
cut the suture. 
U.S. Pat. No. 4,750,901 issued to Molteno discloses a glaucoma implant with 
an elevated peripheral ridge, a subsidiary elevated ridge on the upper 
surface of the implant and a drainage tube which leads from the upper 
surface of the plate to the anterior chamber of the eye. The Molteno 
patent discloses that the tube enters the peripheral ridge to a position 
above the upper surface of the plate and the subsidiary ridge is located 
around the entrance of the tube. The subsidiary ridge is forced against 
Tenon's tissue, i.e., Tenon's capsule, to create an initial bleb cavity 
much smaller in area than the total bleb cavity. The Molteno patent 
discloses that the addition of the subsidiary ridge to the upper surface 
of the plate around the exit of the tube has the effect of providing a 
pressure sensitive one-way valve effect. The Molteno patent also discloses 
that, once the eye recovers from the operation, the increased production 
of the aqueous fluid by the eye raises the pressure in the eye and also 
within the small bleb cavity causing the overlying Tenon's capsule to be 
lifted slightly thereby allowing fluid to gain access to the entire bleb 
cavity. 
In practice however, the Molteno device fails to provide an effective 
sealing surface with Tenon's capsule and the desired one-way valve effect 
does not occur. The main reason that the Molteno device is not functional 
as a one-way valve is that the tissue of Tenon's Capsule stretches so that 
there is little pressure against the subsidiary ridge to provide a sealed 
valve surface. In addition, Tenon's capsule is a thin layer of tissue and 
theoretically can only maintain the orbital tissue pressure of 
approximately 0 to 2 mm mercury to form a seal against the ridge on the 
implant. The orbital tissue pressure can not maintain the pressure within 
the eye of between 4 to 12 mm mercury for a normal eye and up to 20 mm 
mercury for patients that have severe glaucoma with the seal against the 
subsidiary ridge on the Molteno implant. Further, the tissue of Tenon's 
capsule is thin and has greater fluid permeability than other tissues in 
the eye, such as the sclera or conjunctiva, and undesired fluid flow 
passes though the tissue of Tenon's capsule. These forces alone or in 
combination are stronger than the weak seal provided by the Molteno device 
and the Molteno device cannot form a sufficient seal to create the desired 
one-way valve. Instead, the Molteno subsidiary ridge allows fluid to flow 
around it and advances almost directly into the full sized bleb. Thus, the 
Molteno device is not effective in preventing an initial large pressure 
drop in the eye in most cases and post-operative hypotony ensues. 
Therefore, it would be desirable to provide a non-valved glaucoma implant 
device which results in a temporary flow restriction of fluid from exiting 
the anterior chamber of the eye and after sufficient time has elapsed 
creates a patent flow of fluid to/from the anterior chamber of the eye 
without requiring a second surgical operation. 
SUMMARY OF THE INVENTION 
The present invention provides an implant for the treatment of glaucoma 
which creates a temporary seal to restrict the flow of fluid from the 
anterior chamber of the eye and after a period of time provides 
unrestricted flow between the implant and the anterior chamber of the eye. 
The implant comprises a single plate formed of a pliable, elastomeric 
material having a non-valved tube attached to and opening onto a surface 
of the plate. The plate is sutured to the scleral tissue at the forward 
portion of the plate utilizing permanent sutures to keep the plate from 
migrating and impinging on the eye socket tissue or extruding from the eye 
tissue. The plate is covered by a thick flap of Tenon's capsule to be 
encapsulated within a drainage bleb. The attached tube is tunneled through 
the sclera and the cornea and positioned within the anterior chamber to 
provide a drain for aqueous fluid. Because of the pliable construction, 
the device can be implanted with greater ease than previous implants. This 
substantially shortens the time required to perform the surgical procedure 
and to implant such large surface area implants. 
In a unique aspect of the invention, an annular sloped wall surrounds the 
opening of the tube onto the carrier plate. The wall provides a sealing 
surface against the sclera which is similar to an o-ring seal. The pliable 
plate is sutured to the sclera utilizing temporary sutures equally spaced 
around the annular wall to provide and enhance the seal of the wall 
against the sclera. The sutures in the plate force the plate and wall 
against a small area of sclera causing a mechanical seal that allows 
pressure to build up in the reservoir formed by the o-ring configuration 
of the wall and the tube and the anterior chamber of the eye. When the 
pressure in this system is greater than the sutures placed against the 
sclera, the fluid will flow between the surface of the plate and the 
sclera thus maintaining a constant pressure within the eye. The wall 
around the tube forms a temporary seal that allows the fluid to escape. 
Once the pressure in the tube and thus the eye exceeds the pressure 
established by the sutures, drainage of fluid into the periorbital tissues 
is permitted. Once the bleb formation occurs, the temporary sutures around 
the seal are dissolved, absorbed or are removed. After the sutures are 
gone, the plate floats within the bleb, breaks the seal between the wall 
and the sclera, and allows unrestricted flow between the anterior chamber 
and the entire bleb.

DETAILED DESCRIPTION OF THE INVENTION 
FIG. 1 and FIG. 2 illustrate an implant 10 constructed in accordance with 
the present invention positioned within the tissue of an eye 12. The 
relevant structure of the eye 12 will be described briefly below to 
provide background for the anatomical terms incorporated herein, however, 
it should be realized that several anatomical details have been omitted 
for clarity of understanding. The tough outer membrane known as the sclera 
14 covers all of the eye 12 except that portion covered by the cornea 16, 
the thin, transparent membrane which covers the iris 18 and the pupil 20. 
The cornea 16 merges into the sclera 14 at a juncture referred to as the 
sulcus of the sclera or as the limbus 22. The ciliary body 26 begins at 
the limbus 22 and extends along the interior of the sclera 14 and becomes 
the choroid 28. The choroid 28 is a brown vascular membrane which extends 
along the retina back toward the optic nerve. 
It is well-known that aqueous is produced by the ciliary body 26 and 
reaches the anterior chamber 30 formed between the iris 18 and the cornea 
16 through the pupil 20. In a normal eye, the aqueous is removed through 
the trabecular meshwork 32. There the aqueous passes through Schlemm's 
canal 36 and through veins which merge with blood-carrying veins and into 
venous circulation. Intraocular pressure is maintained in the eye 12 by 
the intricate balance of secretion and absorption or outflow of the 
aqueous in the manner described above. Glaucoma results from excessive 
buildup of aqueous fluid in the anterior chamber 30 which produces an 
increase in intraocular pressure. 
The present invention is designed for treatment of glaucoma by facilitating 
the outflow of the aqueous from the anterior chamber 30 of the eye 12. The 
implant 10 comprises a pliable plate 38, also referred to as a pliable 
seton in the ophthalmic field, having oppositely disposed first 39 and 
second 40 curved surfaces, connected to a drainage tube 41 which extends 
into a first region 42 of the eye 12. As illustrated in FIG. 1, the seton 
38 is implanted in a second region 43 of the eye 12 beneath a layer of 
Tenon's capsule 44 mid sutured to the sclera 14. The discharge tube 41 
comprises a first end 46 and a second end 48 wherein the first end 46 is 
attached to the plate 38 adjacent the first surface 39 of the plate 38. 
The second end 48 of the tube 41 extends through the layer of Tenon's 
capsule 44 and through the cornea 16 into a first region 42 of the eye 12 
such as the anterior chamber 30 of the eye 12, to provide fluid 
communication between the first region 42 and the second region 43 of the 
eye 12. A scleral reinforcing element 50, such as a connective tissue 
graft, i.e., a sclera graft, dura mater graft, fascia lata graft, or a 
graft formed from other biocompatible materials, covers the exposed 
portion of the tube 41 located between the Tenon's capsule 44 and the 
sclera 14 and the cornea 16. A large drainage bleb 52 surrounds the seton 
38 and lifts the layer of Tenon's capsule 44 above the sclera 14. The 
seton acts as a permanent bleb controlling stent to inhibit the tendency 
of the body to heal itself which would eliminate the bleb. 
The implant 10 is shown in more detail in FIG. 3 and FIG. 4. The plate 38 
is generally spherical in shape and has a perimeter which is elliptical. 
The surface area of the plate 38 is preferably in the range of 
approximately 100 to 600 mm.sup.2 depending on glaucoma conditions and the 
radius of curvature of the plate 38 is preferably 12 to 14 mm. The plate 
38 includes a raised ridge 56 formed adjacent one of the larger-radius 
perimeter edges of the plate 38, on the first curved spherical surface 39 
of the plate 38. The rounded edge of the plate 38 extending on either side 
of the raised ridge 56, not including that portion of the plate 38 
adjacent the ridge 56, is entirely radiused, tapered and blended so as to 
facilitate insertion as described below. Additionally, the rounded edge of 
the plate 38 is tapered and blended to discourage the unwanted growth of 
scar tissue on the plate 38 which may lock the plate 38 into an unwanted 
position. The rounded edge of the plate 38 provides a smooth surface from 
which the scar tissue preferably slides off and is therefore unable to 
completely anchor onto the plate 38. The second surface 40 of the plate 38 
is curved to conform to the curvature of the eye 12 and the curvature of 
the ridge 56 matches the curvature of the sclera 14. An extension 58 of 
the plate 38 is formed adjacent the ridge 56 in the plate 38 and includes 
two small suture holes 60, 62. The thickness of the plate 38 is preferably 
in the range of 0.5 to 2.0 mm. 
The drainage tube 41 is connected to the plate 38 with adhesive, such as 
Clear Silicone Rubber Adhesive RTV-118 manufactured by General Electric 
Silicone Products of Waterford, N.Y., via a small hole 64 formed in the 
ridge 56 and is bonded to the plate 38 using well-known bonding 
techniques. The first end 46 of the tube 41 thus drains into the recess 
formed at the junction of the ridge 56 and the smooth first surface 39 of 
the plate 38. The plate 38 is preferably formed of silicone elastomer, 
such as SILASTIC.TM., Medical Grade Q7-4765, 65 Shore A, manufactured by 
Dow Corning Corporation of Midland, Mich. or Nusil Corp. of Santa Barbara, 
Calif., although other silicone elastomers in the range of 40-85 Shore A 
and having good elastic memory are also suitable. The silicone elastomer 
is filled with a radiopaque material, such as Barium Sulfate, so that the 
implant is visible in X-rays procedures, thereby allowing patient progress 
monitoring. The drainage tube 41 is preferably a 1.0 to 3.0 French flow 
tube, approximately 10 mm to 15 mm in length, formed of SILASTIC.TM., 
Medical Grade RX-50, also available from Dow Corning Corporation or Nusil 
Corp. of Santa Barbara. 
The present invention can be implanted using known ophthalmological 
surgical techniques and, with reference to FIG. 1, FIG. 2 and FIG. 4, the 
surgical implant procedure will be briefly described. An initial incision 
63 is made in the Tenon's capsule 44 parallel to the limbus 22. The plate 
38 is inserted into the second region 43 of the eye 12 through the initial 
incision 65 and positioned beneath the Tenon's capsule 44 and a portion of 
the rectus muscle 64 or extending totally under one or more muscles, thus 
covering the sclera 14. The plate 38 can be sutured to the sclera 14, or 
alternatively, to the rectus muscle 64 if the sclera 14 is thinned by 
disease, with the suture holes 60, 62. Preferably, nonabsorbable nylon 
sutures are used in the suture holes 60, 62 to secure the plate 38, such 
as 8-O nylon or polypropylene sutures. The drainage tube 41 is tunneled 
out through the sclera 14 and the cornea 16 beneath Tenon's capsule 44 and 
in through an incision 65 in the region of the limbus 22 such that the 
second end 48 of the tube 41 extends into a first region 42, such as the 
anterior chamber 30, of the eye 12. The exposed portion of the drainage 
tube 41 is then covered with a scleral reinforcing element 50. In one 
embodiment, the drainage tube 41 is sutured closed with a temporary 
suture(s) 63, 67 at a location on either side of the sclera reinforcing 
element 50 to prevent any drainage of aqueous prior to formation of the 
bleb tissue 52 over the plate 38. In actual practice, it has been found 
that initially after surgery aqueous fluid will weep through a space 
formed between the yet to be healed incision 65 and the drainage tube 41. 
This weeping of the aqueous fluid through the incision 73 relieves some of 
the fluid pressure until the bleb 52 has formed and the temporary 
suture(s) 63, 67 is/are removed or absorbed by the body. In one 
embodiment, the temporary suture(s) 63 is a dissolvable suture while 
suture 67 is nonabsorbable. In an alternate, but not preferred, 
embodiment, the temporary sutures 63, 67 are removed during a secondary 
procedure, such as a surgical procedure or an ophthalmic laser procedure. 
Both procedures are known to those of skill in the art. 
The formation of the bleb 52 occurs in response to the introduction of the 
plate 38 into the tissue of the second region 43 of the eye 12. The bleb 
52 comprises a thin layer of connective tissue which encapsulates the 
plate 38, and substantially all of the surfaces of the plate 38 contact 
the tissues in the second region 43 of the eye 12, thus lifting the 
Tenon's capsule 44 above the sclera 14 as shown. Typically, bleb 52 
formation occurs in the range of 1 to 8 weeks postoperatively. In the 
above embodiment, an additional surgery can be performed at this time to 
remove the suture(s) 63, 67 from the drainage tube 41 and allow flow of 
aqueous from the anterior chamber 30 to the bleb 52 via the drainage tube 
41. Alternatively, a dissolving suture can be used to seal the drainage 
tube 41. After removal or dissolution of the suture(s) 63, 67 blocking the 
drainage tube 41, the aqueous flow between the tube 41 and bleb 52 is 
advantageously a patent flow, allowing both flow from the anterior chamber 
30 to the bleb 52 and vice versa. This ensures that retrograde non-valved 
flow from the bleb 52 to the anterior chamber 30, occurring in response to 
pressure on the eye 12 from the outside, for example, when the lid is 
forced closed or when the eyeball is pressed on with a finger, does not 
adversely or harmfully affect intraocular pressure within the eye 12. The 
fluid contained in the bleb 52 seeps through the bleb into intercellular 
spaces within the eye 12 and is then removed through surrounding 
capillaries or lymphatics. 
The flexible elastomeric material used to form of the present invention, 
and the size and elliptical shape of the plate 38 allows the implant 10 to 
be inserted much more easily than previously realized with other glaucoma 
treatment implants. During the insertion process, the plate 38 can be 
"folded" in half about the axis of the tube 41 and then inserted through 
the incision 63. Once placed through the incision 63, the plate 38 will 
return to its original shape and can be positioned to cover the sclera 14, 
as described above. Further, the flexible material from which the plate 38 
is formed is soft and pliable which results in much less trauma and 
irritation to the surrounding tissues and vasculature than experienced 
with a rigid plate device. In addition, since the plate 38 can be folded, 
a smaller incision can be made in the Tenon's capsule 44. Thus, the 
pliable plate 38 significantly decreases the surgical procedure length 
while also minimizing tissue and vasculature damage which can occur in the 
insertion process. 
In the preferred embodiment of the implant 10 illustrated in FIG. 5, FIG. 6 
and FIG. 6a, the plate 38 has a profile shape that is generally spherical 
and conforms to the contour of the eye. Preferably, the plate 38 is shaped 
like the profile of an elongated soybean. The soybean shape is similar to 
the elliptical shape of FIG. 3 and FIG. 4 with a rearward portion of the 
plate 38 removed. The soybean shape is preferred as the removed rearward 
portion of the plate 38 prevents the plate 38 from interfering with the 
optic nerve. As indicated above, the surface area of the plate 38 is 
preferably in the range of approximately 100 to 600 mm.sup.2 depending on 
glaucoma conditions. A sloped wall 66 extends from the second surface 40 
of the plate 38 in a forward portion 68 of the plate 38. The dimensions of 
the forward portion 68 of the plate 38 in which the sloped wall 66 extends 
is from 2 to 20 mm in length and from 2 to 20 mm in width. In the 
preferred embodiment, the dimensions of the forward portion 68 of the 
plate are 6 mm in length and 4 mm in width. The dimension of the forward 
portion 68 of the plate 38 could be larger or smaller than those described 
above to accommodate a cavity 82 of the desired dimensions. Preferably, 
the sloped wall 66 has a blended and rounded edge to provide a smooth 
surface from which scar tissue preferably slides off instead of connecting 
to the wall 66. Desirably, the sloped, blended rounded edge of the wall 66 
prevents scar tissue from anchoring onto the implant 10 and permanently 
tethering the plate 38 to the sclera in an undesired position. The sloped 
wall 66 is preferably 25 microns to 5 mm thick, i.e., wide and 50 microns 
to 4 mm in height. The tip of the sloped wall 66 forms a sealing surface 
69 which seals against the sclera 14 upon implantation. 
The drainage tube 41 is connected to the plate 38 of the preferred 
embodiment along a first notch 70 formed in the first surface 39 of the 
plate 38, and then through an opening or small hole 72 formed in the plate 
38 which opens into the second surface 40 of the plate 38. The first end 
46 of the tube 41 is bonded to the plate 38 along the notch 70 with 
adhesive, as described above, and using well-known bonding techniques. The 
tube 41 is bonded to the hole 72 in the plate 38 such that the first end 
46 of the tube 41 is open to the second surface 40 of the plate 38. 
The sloped wall 66 completely surrounds the opening 72 in the second 
surface 40 of the plate 38. Preferably, the sloped wall 66 surrounds an 
area of approximately 0.08 mm.sup.2 -75 mm.sup.2 around the opening 72 in 
the second surface 40 of the plate 38. More preferably, the sloped wall 66 
surrounds an area of approximately 2 mm.sup.2 -14 mm.sup.2 around the 
opening 72 in the second surface 40 of the plate 38. In the preferred 
embodiment, the sloped wall 66 is annular in shape to evenly surround the 
opening 72 and the diameter of the annular shape covered by the wall is 
preferably between approximately 1 mm to 4 ram, but could be as large as 
15 mm. In the preferred embodiment, the annular sloped wall forms a 
concave cupped cavity 82 as defined by the sloped wall 66 and the second 
surface 40 of the plate 38. As will be recognized by one of skill in the 
art, the sloped wall 66 may take on a variety of shapes, such as oval, 
heart shaped, square, rectangular, triangular, etc., in most cases the 
shape surrounds the opening 72 in the second surface 40 of the plate 38. A 
first plurality of suture holes 74-77 are provided around the sloped wall 
66. In the preferred embodiment, the first plurality of sutures holes 
74-77 are evenly spaced around the perimeter of the forward portion 68 of 
the plate 38. A second plurality of suture holes 78, 80 are provided in an 
intermediate 7 portion 81, proximal to the forward portion 68, of the 
plate 38 to enable a surgeon to further secure the plate 38 to the sclera 
14 (FIG. 7). 
Referring also to FIG. 7, when the implant 10 of the preferred embodiment 
is inserted into the eye 12, utilizing the procedure described above, the 
plate 38 is inserted into the second region 43 of the eye and positioned 
beneath the Tenon's capsule 44 and a portion of the rectus muscle (FIG. 
2), thus covering the sclera 14. The tip of the sloped wall 66 creates a 
sealing surface 69 against the sclera 14. Preferably, the seal is similar 
to an o-ring seal. By positioning the implant 10 such that the rectus 
muscle is covering a portion of the implant 10, the rectus muscle helps 
hold the implant 10 against the sclera 14 but does not create any portion 
of the desired seal. The implant 10 lies between the sclera 14 and Tenon's 
capsule 44. Tenon's Capsule 44 lies on the upper surface 39 of the plate 
38, but Tenon's Capsule 44 does not create a portion of the desired seal. 
During implantation, the plate 38 is sutured to the sclera 14 utilizing 
both absorbable and nonabsorbable sutures in a first plurality of suture 
holes 74-77 and absorbable or nonabsorbable sutures in a second plurality 
of suture holes 78, 80. The first plurality of suture holes 74-77 are 
spaced around the sloped wall 66 to provide an enhanced seal of the wall 
66 against the sclera 14. The second plurality of sutures 78,80 on the 
immediate portion 81 of the plate 38 assist in tethering the plate 38 to 
the sclera 14. After implantation, the aqueous fluid from the first region 
42 of the eye 12 drains through the drainage tube 41 into the concave 
cupped cavity 82 which is sealed against the sclera 14. The sutures 74-77 
assist in sealing the cupped cavity 82 against the sclera 14 at the 
sealing surface 69; therefore, the aqueous fluid is unable to escape from 
the cavity 82. Once the cavity 82 is filled with fluid, the fluid pressure 
within the sealed cavity 82 prevents additional fluid from draining from 
the first region 42 of the eye 12 into the cavity 82, thereby preventing 
low pressure from occurring in the second region 42 of the eye 12. As will 
be recognized by those of skill in the art, the dimensions of the cavity 
82 are selected to define the flow of fluid that can exit the first region 
42 of the eye 12, before the flow is restricted, without creating a 
pressure drop in the eye 12. Therefore, the sealing of the wall 66 of the 
plate 38 against the sclera 14 creates a sealed cavity 82 which 
temporarily occludes the drainage of aqueous fluid from the first region 
42 of the eye 12. This o-ring seal effect is achieved both by the design 
of the implant 10 and the tension produced by the absorbable and 
nonabsorbable sutures placed by the surgeon in the first plurality of 
suture holes 74-77 and/or the second plurality of suture holes 78, 80. The 
sutures hold the implant 10 against the sclera 14 with the necessary 
tension desired by the surgeon. In a preferred embodiment, the tension 
level of the sutures is set to withstand pressures of up to 10-20 mm 
mercury. Preferably, the fluid pressure in the first region 42 of the eye 
12 reaches an equilibrium pressure with the pressure in the cavity 82 
while scar tissue in the eye forms a bleb 52. This equilibrium pressure is 
less than the pressure applied by the sutures. Further, some fluid in the 
cavity 82 may be absorbed by the sclera tissue below the cavity 82. This 
absorption of fluid will help maintain the desired equilibrium pressure. 
When the pressure in the cavity 82 and the first region 42 of the eye 12 
exceed the tension of the sutures as applied by the surgeon, fluid will 
leak around the o-ring seal and maintain the eye pressure determined by 
the surgeon. This prevents the eye pressure from exceeding a specific 
value, as determined by the tension of the sutures as applied by the 
surgeon, which could cause damage to the eye. If the fluid pressure does 
not exceed the tension of the sutures, the o-ring type seal will maintain 
the fluid pressure within the cavity 82. 
In the preferred embodiment, the temporary sutures are dissolvable sutures. 
In an alternate, but not preferred embodiment, the temporary sutures ewe 
removed during a secondary procedure, such as a surgical procedure or a 
laser procedure, after scar tissue formation. In the preferred embodiment, 
the temporary sutures are selected such that the sutures dissolve after 
the formation of the scar tissue bleb. The sutures can be absorbed at any 
time postoperatively from 1 day up to 8 weeks. Preferably, the sutures are 
dissolved in 1 to 6 weeks postoperatively. In the preferred embodiment, 
the dissolving sutures are 8-O Vicryl. As illustrated in FIG. 8, after the 
bleb 52 forms, the temporary sutures are removed or absorbed by the body, 
the fluid pressure in the cupped cavity 82 pushes the plate 38 off the 
surface of the sclera 14 and the seal formed by the sealing surface 69 of 
the sloped wall 66 against the sclera 14 is broken. The bleb 52 eventually 
fills with fluid and the seton 38 floats within the fluid in the bleb 52 
and maintains the bleb shape. In a preferred embodiment, permanent sutures 
are utilized in the suture holes 78, 80 on the plate 38 to keep the 
intermediate end 81 of the seton 38 tethered to the sclera 14 thus 
preventing the plate 14 from impinging on the eye socket and other tissues 
in the eye 12 or from extruding. Preferably, with the intermediate end 81 
of the plate 38 permanently sutured to the sclera 14, a rearward end 84 of 
the plate 38 pivots off of the sclera 14. In one embodiment, the tethered 
plate 38 acts like a leaflet valve. Once the o-ring type seal of the wall 
66 is broken, patent flow between the second region 43 of the eye 12, such 
as the bleb 52, and the first region 42 of the eye 12, such as the 
anterior chamber 30, is maintained. 
As shown in FIGS. 9a through 9c, a variety of configurations of the sloped 
wall 66 are possible. Although four configurations are illustrated, one 
skilled in the art will recognize that various other embodiments could be 
constructed. In the embodiment illustrated in FIG. 9a, the concave cavity 
82 formed by the sloped wall 66 and the second surface 40 of the plate 38 
is located in the rearward end 84 of the plate 38. In this embodiment, the 
tube 41 is attached along the second surface 40 of the plate 38. The tube 
41 preferably enters the cavity 82 through a hole (not shown) in the 
sloped wall 66. The first end 46 of the tube 41 is open to the cupped 
cavity 82 formed by the sloped wall 66 and the second surface 40 of the 
plate 38. In this embodiment, the second plurality of suture holes 78-80 
are located on the perimeter of the forward portion 68 of the plate 38, 
while the first plurality of suture holes 74-77 are located on a rearward 
portion 84 of the plate 38 surrounding the sloped wall 66. Preferably, the 
plate 38 is attached to the sclera by temporary sutures in suture holes 
74-77 and nonabsorbable sutures in the suture holes 78, 80. Preferably, 
after bleb formation, the temporary sutures in the rearward portion 84 of 
the plate 38 dissolve and the rearward portion 68 of the plate 38 floats 
in the bleb while the forward portion of the plate 38 remains attached to 
the sclera. 
In the embodiment of FIG. 9b, a plurality of cavities defined by the sloped 
walls 66 are formed on the second surface 40 of the plate 38. First 86 and 
second 88 cavities are connected by a second flexible elastomeric 
connection tube 90. Preferably, the first end 46 of the drainage tube 41 
is open to the first cavity 86. A first end 92 of the connection tube 90 
is open to a hole in the first cavity 86. A second end 94 of the 
connection tube 90 is open to a hole in the second cavity 88. Once both 
the first 86 and second 88 cavities are filled with aqueous fluid, the 
fluid pressure in the cavities 86, 88 prevents additional fluid from 
draining from the anterior chamber 30 of the eye 12. In this embodiment, a 
third plurality of suture holes 91, 93 are located on the perimeter of the 
rearward portion 84 of the plate 38. The plate 38 is attached to the 
sclera by temporary sutures in the first and third plurality of suture 
holes 74-77 and 91, 93 and nonabsorbable sutures in the second plurality 
of suture holes 78, 80. Preferably, after bleb formation, the temporary 
sutures are absorbed by the body, or alternatively removed, and the 
rearward portion 84 and a portion of the forward portion 68 of the plate 
38 float while the intermediate portion 81 of the plate 38 remains 
attached to the sclera. 
In the embodiment of FIG. 9c, one large cavity 96 is formed below 
substantially the entire second surface 40 of the plate 38 by the addition 
of the sloped wall 66 around the entire perimeter of the second surface 40 
of the plate 38. Permanent sutures are utilized in the suture holes 98 to 
affix the forward end 68 of the plate 38 to the sclera. A plurality of 
suture holes 100 are evenly dispersed around the remaining perimeter of 
the plate 38. Temporary sutures are used in suture holes 100 to 
temporarily seal the majority of the perimeter of the plate 33. When the 
temporary sutures 100 dissolve or alternatively are removed, the rearward 
portion 84 of the plate 38 lifts off of the sclera 14 to enable patent 
flow of the aqueous humor from the first region 42 of the eye 12 into the 
bleb 52. 
In the embodiment of FIG. 9d, the shape of the implant 110 is modified to 
form a cavity 112 within the plate, or seton, 114, rather than including a 
sloped wall extending from a second surface 116 of the plate 114. The 
plate 114 preferably is spherically shaped to match the convex anatomy of 
the eye and has a matching surface 118 around the perimeter of the concave 
second surface 116 of the plate 114. In a center portion 120 of the plate 
114, the plate 114 is shaped such that a hemispherical cupped concave 
cavity 122 is formed around an opening 124 of the tube 41 in the second 
surface 116 of the plate 114. In an alternate embodiment (not shown), the 
plate 114 does not have to include a hemispherical concave cavity 122 
formed in the plate 114. Rather, since the plate 114 is pliable, the plate 
114 bends to accommodate the physical anatomical convex shape of the 
patient's eye 12 such that the matching surface 118 around the perimeter 
of plate is flush with the surface of the sclera 14. A permanent suture is 
used in suture hole 125 and a temporary suture is used in suture hole 126 
to hold the sealing surface 127 of the seton 114 against the surface of 
the sclera 14. A sealing surface 127 on the matching surface 118 of the 
plate is formed against the surface of the sclera 14 which temporarily 
occludes the flow of the aqueous out of the cavity 122. In the embodiment 
of the platen 114 where a physical cavity 122 is not formed in the plate, 
the pliable nature of the sutured plate 114 will naturally form a cavity 
122 of sufficient size to hold the desired amount of fluid. As illustrated 
in FIG. 9e, when the temporary suture in suture hole 126 is removed or 
absorbed by the body, a rearward portion 128 of the seton 114 moves away 
from the sclera 14 breaking the s:al of the sealing surface 127 against 
the sclera 14, so that non-valved patent flow of the aqueous can occur. 
Another alternative embodiment of the present invention is illustrated in 
FIG. 10 which incorporates a plurality of holes, sometimes referred to as 
fenestrations, 130 in the rearward portion 84 of the plate 38 which does 
not contain the cavity 82. As illustrated in FIG. 10, the plate 38 has 
essentially the same shape as the embodiments illustrated in FIGS. 5-6, 
with the addition of a plurality of aligned holes 130 in the rearward 
portion 84 of the plate 38. The holes 130 do not interfere with the sealed 
cavity 82 in the forward portion 68 of the plate 38. However, in the 
preferred embodiment, once the sutures in the first plurality of suture 
holes 74-77 around the sealed cavity 82 or the second plurality of suture 
holes 78, 80 dissolve or are removed and the rearward end 84 of the plate 
38 is able to float within the bleb, each of the holes 130 will form a 
dimple in the bleb by permitting scar tissue growth through each of the 
holes 130. The overall height of the bleb will be significantly decreased 
in both the upper and lower directions as the bleb is pulled towards the 
plate 38 by the growth of scar tissue through each of the holes 130. 
Preferably, the holes 130 are between 50 microns and 10 mm in diameter. As 
the number of holes 130 in the plate 38 increases, preferably the diameter 
of the holes 130 decreases proportionally, but will remain within the 
above range of preferable diameters. As the number of holes 130 increase 
in the seton 38, the number of dimples in the resulting drainage bleb will 
increase proportionately until the horizontal area of the plate 38 and the 
diameter of the holes 130 limit the addition of the other holes 130. 
Although the invention has been described with reference to specific 
embodiments, the description is intended to be illustrative of the 
invention and is not intended to be limiting. Various modifications and 
applications may occur to those skilled in the art without departing from 
the true spirit and scope of the invention as defined in the appended 
claims.