U.S. patent application number 10/897819 was filed with the patent office on 2004-12-23 for stent device and method for treating glaucoma.
Invention is credited to Brown, Reay H., Lynch, Mary G..
Application Number | 20040260228 10/897819 |
Document ID | / |
Family ID | 22447552 |
Filed Date | 2004-12-23 |
United States Patent
Application |
20040260228 |
Kind Code |
A1 |
Lynch, Mary G. ; et
al. |
December 23, 2004 |
Stent device and method for treating glaucoma
Abstract
Stent devices and a method for continuously facilitating the
flow of aqueous humor through Schlemm's canal where post-operative
patency can be maintained with an indwelling stent device. The
stent devices provide uni- or bi-directional flow of aqueous humor
within and through Schlemm's canal.
Inventors: |
Lynch, Mary G.; (Atlanta,
GA) ; Brown, Reay H.; (Atlanta, GA) |
Correspondence
Address: |
SUTHERLAND ASBILL & BRENNAN LLP
999 PEACHTREE STREET, N.E.
ATLANTA
GA
30309
US
|
Family ID: |
22447552 |
Appl. No.: |
10/897819 |
Filed: |
July 23, 2004 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10897819 |
Jul 23, 2004 |
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10269636 |
Oct 11, 2002 |
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6783544 |
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10269636 |
Oct 11, 2002 |
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09557849 |
Apr 26, 2000 |
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6464724 |
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60131030 |
Apr 26, 1999 |
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Current U.S.
Class: |
604/8 |
Current CPC
Class: |
A61F 9/00781 20130101;
A61M 2210/0612 20130101; A61M 25/0074 20130101; A61F 2250/0067
20130101; A61F 9/0017 20130101; A61F 2230/0052 20130101; A61F
2230/0008 20130101; A61M 25/007 20130101; A61M 25/0068
20130101 |
Class at
Publication: |
604/008 |
International
Class: |
A61M 005/00 |
Claims
1-23. (Canceled)
24. A stent device for use in the eye to relieve excess intraocular
pressure by facilitating drainage through and within Schlemm's
canal, comprising a thin body of biocompatible material of a length
and shape adapted to be wholly retained within a portion of
Schlemm's canal, wherein the device can move between a first
insertion position and a second expanded stenting position when
positioned in a desired location of Schlemm's canal.
25. The stent device of claim 24, wherein the body comprises a
multisided structure at least at one position along the length of
the body.
26. The stent device of claim 24, wherein body comprises a luminal
tubular mesh.
27. The stent device of claim 24, wherein the body has a curve
having a radius which approximates the radius of Schlemm's canal of
a human eye, wherein the radius is between about 3 mm and 10
mm.
28. The stent device of claim 27, wherein said body has a curve
having a radius of about 6 mm.
29. The stent device of claim 24, wherein said body has an outer
diameter of about 0.1 to 0.5 mm.
30. The stent device of claim 29, wherein said body has an outer
diameter of about 0.3 mm.
31. The stent device of claim 24, wherein said body has a length of
about 1 mm to 40 mm.
32. The stent device of claim 31, wherein said body has a length of
about 20 mm.
33. The stent device of claim 24, wherein the body provides for
drainage in both directions along Schlemm's canal.
34. The stent device claim 24, wherein the body has a plurality of
fenestrations therein that allow the passage of fluid into
Schlemm's canal.
35. The stent device of claim 24, wherein the body is curved to
define a trough-like, partially open channel along at least some of
the length of the body open toward the collecting channels of the
eye.
36. The stent device of claim 24, wherein the stent further
comprises a therapeutic agent.
37. A method for the surgical treatment of glaucoma, comprising,
performing a trabeculotomy through a conjunctival flap made at the
limbus; developing a partial thickness scleral flap; radially
incising the junction between the angle tissue and the sclera,
which is surgically extended until Schlemm's canal is entered
posteriorly, and placing one or more of the stent devices of any of
claims 24-36 within Schlemm's canal.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims the benefit of U.S. Provisional
Application No. 60/131,030, filed Apr. 26, 1999.
TECHNICAL FIELD
[0002] The present invention is generally directed to a surgical
treatment for glaucoma, and relates more particularly to a device
and method for continuously maintaining the patency of Schlemm's
canal with a trough-like, indwelling stent which can be surgically
placed to traverse at least a portion of the circumference of the
canal and to facilitate the drainage of aqueous humor
therethrough.
BACKGROUND OF THE INVENTION
[0003] Glaucoma is a significant public health problem, because
glaucoma is a major cause of blindness. The blindness that results
from glaucoma involves both central and peripheral vision and has a
major impact on an individual's ability to lead an independent
life.
[0004] Glaucoma is an optic neuropathy (a disorder of the optic
nerve) that usually occurs in the setting of an elevated
intraocular pressure. The pressure within the eye increases and
this is associated with changes in the appearance ("cupping") and
function ("blind spots" in the visual field) of the optic nerve. If
the pressure remains high enough for a long enough period of time,
total vision loss occurs. High pressure develops in an eye because
of an internal fluid imbalance.
[0005] The eye is a hollow structure that contains a clear fluid
called "aqueous humor." Aqueous humor is formed in the posterior
chamber of the eye by the ciliary body at a rate of about 2.5
microliters per minute. The fluid, which is made at a fairly
constant rate, then passes around the lens, through the pupillary
opening in the iris and into the anterior chamber of the eye. Once
in the anterior chamber, the fluid drains out of the eye through
two different routes. In the "uveoscleral" route, the fluid
percolates between muscle fibers of the ciliary body. This route
accounts for approximately ten percent of the aqueous outflow in
humans. The primary pathway for aqueous outflow in humans is
through the "canalicular" route that involves the trabecular
meshwork and Schlemm's canal.
[0006] The trabecular meshwork and Schlemm's canal are located at
the junction between the iris and the sclera. This junction or
corner is called "the angle." The trabecular meshwork is a
wedge-shaped structure that runs around the circumference of the
eye. It is composed of collagen beams arranged in a
three-dimensional sieve-like structure. The beams are lined with a
monolayer of cells called trabecular cells. The spaces between the
collagen beams are filled with an extracellular substance that is
produced by the trabecular cells. These cells also produce enzymes
that degrade the extracellular material. Schlemm's canal is
adjacent to the trabecular meshwork. The outer wall of the
trabecular meshwork coincides with the inner wall of Schlemm's
canal. Schlemm's canal is a tube-like structure that runs around
the circumference of the cornea. In human adults, Schlemm's Canal
is believed to be divided by septa into a series of autonomous,
dead-end canals.
[0007] The aqueous fluid travels through the spaces between the
trabecular beams, across the inner wall of Schlemm's canal into the
canal, through a series of about 25 collecting channels that drain
from Schlemm's canal and into the episcleral venous system. In a
normal situation, aqueous production is equal to aqueous outflow
and intraocular pressure remains fairly constant in the 15 to 21
mmHg range. In glaucoma, the resistance through the canalicular
outflow system is abnormally high.
[0008] In primary open angle glaucoma, which is the most common
form of glaucoma, the abnormal resistance is believed to be along
the outer aspect of trabecular meshwork and the inner wall of
Schlemm's canal. It is believed that an abnormal metabolism of the
trabecular cells leads to an excessive build up of extracellular
materials or a build up of abnormally "stiff" materials in this
area. Histopathology of glaucoma eyes also demonstrates a collapse
of Schlemm's canal. Primary open angle glaucoma accounts for
approximately eighty-five percent of all glaucoma. Other forms of
glaucoma (such as angle closure glaucoma and secondary glaucomas)
also involve decreased outflow through the canalicular pathway but
the increased resistance is from other causes such as mechanical
blockage, inflammatory debris, cellular blockage, etc.
[0009] With the increased resistance, the aqueous fluid builds up
because it cannot exit fast enough. As the fluid builds up, the
intraocular pressure (IOP) within the eye increases. The increased
IOP compresses the axons in the optic nerve and also may compromise
the vascular supply to the optic nerve. The optic nerve carries
vision from the eye to the brain. Some optic nerves seem more
susceptible to IOP than other eyes. While research is investigating
ways to protect the nerve from an elevated pressure, the only
therapeutic approach currently available in glaucoma is to reduce
the intraocular pressure.
[0010] The clinical treatment of glaucoma is approached in a
step-wise fashion. Medication often is the first treatment option.
Administered either topically or orally, these medications work to
either reduce aqueous production or they act to increase outflow.
Currently available medications have many serious side effects
including: congestive heart failure, respiratory distress,
hypertension, depression, renal stones, aplastic anemia, sexual
dysfunction and death. Compliance with medication is a major
problem, with estimates that over half of glaucoma patients do not
follow their correct dosing schedules.
[0011] When medication fails to adequately reduce the pressure,
laser trabeculoplasty often is performed. In laser trabeculoplasty,
thermal energy from a laser is applied to a number of noncontiguous
spots in the trabecular meshwork. It is believed that the laser
energy stimulates the metabolism of the trabecular cells in some
way, and changes the extracellular material in the trabecular
meshwork. In approximately eighty percent of patients, aqueous
outflow is enhanced and IOP decreases. However, the effect often is
not long lasting and fifty percent of patients develop an elevated
pressure within five years. The laser surgery is not usually
repeatable. In addition, laser trabeculoplasty is not an effective
treatment for primary open angle glaucoma in patients less than
fifty years of age, nor is it effective for angle closure glaucoma
and many secondary glaucomas.
[0012] If laser trabeculoplasty does not reduce the pressure
enough, then filtering surgery is performed. With filtering
surgery, a hole is made in the sclera and angle region. This hole
allows the aqueous fluid to leave the eye through an alternate
route.
[0013] The most commonly performed filtering procedure is a
trabeculectomy. In a trabeculectomy, a posterior incision is made
in the conjunctiva, the transparent tissue that covers the sclera.
The conjunctiva is rolled forward, exposing the sclera at the
limbus. A partial thickness scleral flap is made and dissected
half-thickness into the cornea. The anterior chamber is entered
beneath the scleral flap and a section of deep sclera and
trabecular meshwork is excised. The scleral flap is loosely sewn
back into place. The conjunctival incision is tightly closed.
Post-operatively, the aqueous fluid passes through the hole,
beneath the scleral flap and collects in an elevated space beneath
the conjunctiva. The fluid then is either absorbed through blood
vessels in the conjunctiva or traverses across the conjunctiva into
the tear film.
[0014] Trabeculectomy is associated with many problems. Fibroblasts
that are present in the episclera proliferate and migrate and can
scar down the scleral flap. Failure from scarring may occur,
particularly in children and young adults. Of eyes that have an
initially successful trabeculectomy, eighty percent will fail from
scarring within three to five years after surgery. To minimize
fibrosis, surgeons now are applying antifibrotic agents such as
mitomycin C (MMC) and 5-fluorouracil (5-FU) to the scleral flap at
the time of surgery. The use of these agents has increased the
success rate of trabeculectomy but also has increased the
prevalence of hypotony. Hypotony is a problem that develops when
aqueous flows out of the eye too fast. The eye pressure drops too
low (usually less than 6.0 mmHg); the structure of the eye
collapses and vision decreases.
[0015] Trabeculectomy creates a pathway for aqueous fluid to escape
to the surface of the eye. At the same time, it creates a pathway
for bacteria that normally live on the surface of the eye and
eyelids to get into the eye. If this happens, an internal eye
infection can occur called endophthalmitis. Endophthalmitis often
leads to permanent and profound visual loss. Endophthalmitis can
occur anytime after trabeculectomy. The risk increases with the
thin blebs that develop after MMC and 5-FU. Another factor that
contributes to infection is the placement of a bleb. Eyes that have
trabeculectomy performed inferiorly have about five times the risk
of eye infection than eyes that have a superior bleb. Therefore,
initial trabeculectomy is performed superiorly under the eyelid, in
either the nasal or temporal quadrant.
[0016] In addition to scarring, hypotony and infection, there are
other complications of trabeculectomy. The bleb can tear and lead
to profound hypotony. The bleb can be irritating and can disrupt
the normal tear film, leading to blurred vision. Patients with
blebs generally cannot wear contact lenses. All of the
complications from trabeculectomy stem from the fact that fluid is
being diverted from inside the eye to the external surface of the
eye.
[0017] When trabeculectomy doesn't successfully lower the eye
pressure, the next surgical step often is an aqueous shunt device.
An aqueous shunt device of the prior art is a silicone tube that is
attached at one end to a plastic (polypropylene or other synthetic)
plate. With an aqueous shunt device, an incision is made in the
conjunctiva, exposing the sclera. The plastic plate is sewn to the
surface of the eye posteriorly, usually over the equator. A full
thickness hole is made into the eye at the limbus, usually with a
needle. The tube is inserted into the eye through this hole. The
external portion of the tube is covered with either donor sclera or
pericardium. The conjunctiva is replaced and the incision is closed
tightly. Many problems exist with the current technology of aqueous
shunt devices including scarring, failure, hypotony, and
infection.
[0018] Some prior art references for glaucoma management have been
directed at Schlemm's canal, but these have not involved the
placement of long-term, indwelling stents. For example, U.S. Pat.
No. 5,360,399 teaches the placement of a portion of a plastic or
steel tube in Schlemm's canal with injection of a viscous material
through the tube to hydraulically dissect the trabecular meshwork.
The tube is removed from the canal following injection.
Furthermore, relative to that portion within Schlemm's canal, the
'399 device has a larger diameter injection cuff element, which
serves as an adapter for injection and irrigation. Therefore, this
device is not adapted for permanent placement within Schlemm's
canal.
[0019] A need exists, then, for a more physiologic system to
enhance the drainage of aqueous fluid through Schlemm's canal.
Enhancing aqueous flow directly into Schlemm's canal would minimize
scarring since the angle region is populated with a single line of
nonproliferating trabecular cells. Enhancing aqueous flow directly
into Schlemm's canal would minimize hypotony since the canal is
part of the normal outflow system and is biologically engineered to
handle the normal volume of aqueous humor. Enhancing aqueous flow
directly into Schlemm's canal would eliminate complications such as
endophthalmitis and leaks.
SUMMARY OF THE INVENTION
[0020] The present invention is directed to a novel stent and an
associated surgical method for the surgical correction of glaucoma
in which the stent is placed into Schlemm's canal to expand the
canal's dimensions and maintain its patency. The present invention
therefore facilitates the normal physiologic pathway for drainage
of aqueous humor into and through Schlemm's canal. The present
invention is further directed to providing a permanent, indwelling
stent within Schlemm's canal for glaucoma management.
BRIEF DESCRIPTION OF THE DRAWINGS
[0021] FIG. 1 is an illustration showing a side view of one
embodiment of the present invention, in which the inventive stent
is comprised of tubular elements traversing the circumference of
Schlemm's canal.
[0022] FIG. 2 is an illustration showing another embodiment of the
present invention, in which the inventive stent is comprised of
luminal mesh tubular elements.
[0023] FIG. 3 is an illustration showing another embodiment of the
present invention in which the inventive stent is comprised of
elements that are partially tubular and partially open in their
configuration.
[0024] FIG. 4 is an illustration showing the anatomic details of
the human eye.
[0025] FIG. 5 is an illustration showing the anatomic relationships
(not to scale) of the surgical placement of an exemplary embodiment
of the present invention.
DETAILED DESCRIPTION OF PRESENT INVENTION
[0026] The present invention provides an aqueous humor stent device
to be placed within a portion of Schlemm's canal of the eye as an
indwelling implant to expand and maintain the patency of the canal,
in which the stent device comprises a body portion shaped to be
wholly received within Schlemm's canal to facilitate the natural
drainage of aqueous humor to the collecting channels of the
eye.
[0027] The present invention also provides embodiments of an
inventive stent comprising a thin body of biocompatible material of
a length and shape adapted to be wholly received within Schlemm's
canal and to extend within a portion of the circumference of
Schlemm's canal, and having a channel therein to facilitate the
passage of aqueous humor into and through Schlemm's canal to the
collecting channels. The invention contemplates many different
configurations for a stent device, provided that each assists in
channeling aqueous humor throughout Schlemm's canal, such as by
providing a lumen, trough, wick or capillary action. In some
embodiments of the invention, the body of the stent can move
between a first insertion position and a second expanded stenting
position when in a desired location of the canal.
[0028] The present invention also provides methods of use of the
stent devices. One embodiment of the present invention is directed
to a surgical method to implant the inventive stent into a portion
of the circumference of Schlemm's canal. The device extending into
Schlemm's canal may be fashioned from a flexible, porous or
non-porous, biologically inert material to approximately equal a
portion of the radius, curvature, and diameter of Schlemm's canal.
All or parts of the device may be tubular or non-tubular, and
fenestrated or non-fenestrated. The device may further be sized to
allow placement through all or some of the circumference of
Schlemm's canal.
[0029] Traditional glaucoma teaching states that Schlemm's canal in
an adult is divided by septa into separate canals, rendering the
complete passage of a suture impossible. Preliminary studies on
adult human eye bank eyes have shown that Schlemm's canal is,
indeed, patent. A suture can be passed through the entire
circumference of the canal. It has not been heretofore determined
that Schlemm's canal is patent throughout its circumference in
normal individuals, as opposed to being divided by septa into
multiple dead end canals. The present invention utilizes this
knowledge to create and maintain patency within Schlemm's canal
with the present stent devices.
[0030] One embodiment of the present invention is illustrated in
FIG. 1, in which the stent device 100 is shown in a side view. The
stent device 100 is comprised of a tubular body portion 10 defining
a lumen 5 which may have solid tubular walls or may contain a
plurality of fenestrations 15 communicating between the lumen 5 and
the exterior. The body portion has a pre-formed curvature with a
radius r which approximates the 6 mm radius of Schlemm's canal of
an adult human eye. The cross-sectional diameter of the body
portion 10 is sized to be fully received within Schlemm's canal.
The body portion 10 may be either an enclosed tubular or multisided
structure, or it may be a flat, angular, or curved open structure,
or some combination of the above when cross-sectioned at different
sites along the entirety of its length. The fenestrations 15 may be
placed along any portion of the device 100 to facilitate the
passage of fluid therethrough.
[0031] Other examples of embodiments of the present invention are
shown in FIGS. 2-3. FIG. 2 shows an embodiment of the inventive
stent in which the device 100 comprises a luminal tubular mesh in
its configuration, again with a pre-formed curvature with a radius
r to approximate the 6 mm radius of Schlemm's canal and a
cross-sectional diameter of the body portion 10 sized to be fully
received within Schlemm's canal.
[0032] FIG. 3 shows an embodiment of the inventive stent in which
the body portion 10 is open and curved throughout its length in a
trough-like channel, again with a pre-formed curvature with a
radius r to approximate the 6 mm radius of Schlemm's canal and a
cross-sectional diameter of the body portion 10 sized to be fully
received within Schlemm's canal.
[0033] As the inventive device is a long-term implant, it can be
fabricated from a material that will be innocuous to the tissues
and fluids with which it is in contact. It is preferable that the
device not be absorbed, corroded, or otherwise structurally
compromised during its in situ tenure. Moreover, it is equally
preferable that the eye tissues and the aqueous remain
non-detrimentally affected by the presence of the implanted device.
A number of materials are available to meet the engineering and
medical specifications for the stents. In the exemplary embodiments
of the present invention, the stent device 100 is constructed of a
biologically inert, flexible material such as silicone or similar
polymers. Alternate materials might include, but are not limited
to, thin-walled polytetrafluoroethylene, polypropylene or other
polymers. Other metals and alloys known in the art of stenting can
also be used, such as stainless steel, titanium or nitinol. The
stent can also be fabricated with therapeutic agents that migrate
from the device over time.
[0034] In the embodiments shown in FIGS. 1-5, the body portion 10
may have a pre-formed curve to approximate the 6.0 mm radius of
Schlemm's canal in a human eye. The body portion 10 may be of
sufficient length to extend through any length of the entire
circumference of Schlemm's canal, with a total length for the body
portion 10 of about 1.0 mm to 40 mm, or about 2 mm to 20 mm, or
about 5 mm to permit circumferential placement through Schlemm's
canal. The diameter or width of the body portion 10 can be sized to
yield an internal diameter of between 0.1 mm and 0.5 mm, preferably
about 0.2 mm and an external diameter of between 0.1 mm and 0.5 mm,
or about 0.3 mm, for a tubular or curved stent, or a comparable
maximal width for a stent with a multiangular configuration. The
body portion 10 may contain a plurality of fenestrations to allow
fluid egress, arranged to prevent occlusion by the adjacent walls
of Schlemm's canal, particularly in the direction of the collecting
channels.
[0035] The surgical anatomy relevant to the present invention is
illustrated in FIG. 4. Generally, FIG. 4 shows the anterior chamber
35, Schlemm's canal 30, the iris 40, cornea 45, trabecular meshwork
50, collecting channels 55, episcleral veins 60, pupil 65, and lens
70. FIG. 5 illustrates the surgical placement of the exemplary
embodiment of the present invention, with the relevant anatomic
relationships. It should be noted that the inventive device is
designed so that placement of multiple stents within Schlemm's
canal 30 can result in a near-circumferential traverse of Schlemm's
canal 30. The surgical incision into Schlemm's canal 30 is closed,
with no direct external communication with the stent device 100
intended.
[0036] The surgical procedure necessary to insert the device may
include all or some of the following steps: A conjunctival incision
is made. A partial thickness scleral flap is then created and
dissected half-thickness into clear cornea. The posterior aspect of
Schlemm's canal is identified and the canal is entered posteriorly.
The anterior chamber may be deepened with injection of a
viscoelastic or miotic agent. A balloon catheter, such as described
in U.S. Ser. No. ______, filed Apr. 26, 2000, may be introduced
into Schlemm's canal, and inflated to dilate portions of Schlemm's
canal, followed by the selective deflation of the balloon and
placement of one or more stent devices into Schlemm's canal.
Alternately, the stent devices may be introduced directly on a
balloon catheter device. Therefore, a plurality of stent segments
may be placed at selected locations along the circumference of
Schlemm's canal. Any residual stent material is trimmed, and the
scleral flap and conjunctival wound are closed in a conventional
manner.
[0037] While the above-described embodiments are exemplary, the
invention contemplates a wide variety of shapes and configurations
of the stent to provide fluid communication between the anterior
chamber and Schlemm's canal and to the collecting channels. The
above-described embodiments are therefore not intended to be
limiting to the scope of the claims and equivalents thereof.
* * * * *