U.S. patent number RE35,390 [Application Number 08/393,156] was granted by the patent office on 1996-12-03 for pressure relieving device and process for implanting.
Invention is credited to Stewart G. Smith.
United States Patent |
RE35,390 |
Smith |
December 3, 1996 |
Pressure relieving device and process for implanting
Abstract
This invention involves a porous device for implantation in the
scleral tissue of the eye to relieve the intraocular pressure of
glaucoma and a method for surgically implanting the device.
Inventors: |
Smith; Stewart G. (Yorklyn,
DE) |
Family
ID: |
27389862 |
Appl.
No.: |
08/393,156 |
Filed: |
February 17, 1995 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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170664 |
Dec 16, 1993 |
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925726 |
Aug 4, 1992 |
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Reissue of: |
437840 |
Nov 17, 1989 |
04946436 |
Aug 7, 1990 |
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Current U.S.
Class: |
604/8 |
Current CPC
Class: |
A61F
9/00781 (20130101) |
Current International
Class: |
A61F
9/007 (20060101); A61M 005/00 (); A61F
002/14 () |
Field of
Search: |
;604/8-10,289,294
;623/4 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Jones; Mary Beth
Attorney, Agent or Firm: Wolfson; Herbert M.
Parent Case Text
.Iadd.This application is a continuation of Serial No. 08/170,664,
filed Dec. 16, 1993, now abandoned, which is a continuation of
07/925,726 filed Aug. 4, 1992, now abandoned, which is a reissue of
07/437,840, filed Nov. 17, 1989, now U.S. Pat. No.
4,946,436..Iaddend.
Claims
What is claimed is:
1. A device for relieving intraocular pressure comprises a body
portion .Iadd.and wall portions in the form of a hexahedron; at
least the body portion .Iaddend.composed of a biocompatible porous
material; said device adapted to be implanted within the scleral
tissue of the eye with at least one edge of the device at an
opening of, with no substantial extension into, the anterior
chamber and adjacent to the area where the sclera makes the
transition into clear cornea of the eye; the pores of the body
portion are of such size and quantity as to permit drainage of
fluid from the anterior chamber to the scleral tissue without
collapse of the anterior chamber.
2. A device as in claim 1 wherein .[.one face of the hexahedron
is.]. .Iadd.said body portion has a first surface, said first
surface of said body portion being .Iaddend.sloped to overlie the
opening into the anterior chamber to direct fluid from the anterior
chamber into the body portion of the device.
3. A device as in claim 1 wherein .[.at least one edge of one wall
portion of the device.]. at least one edge of .[.one wall
portion.]. .Iadd.the top surface .Iaddend.of the device is extended
for anchoring the device in position.
4. A device as in claim 1 wherein the .Iadd.three .Iaddend.edges of
.[.three wall portions of.]. the .Iadd.top surface of the
.Iaddend.device, other than .[.an.]. .Iadd.the .Iaddend.edge at the
opening of the anterior chamber, are extended for anchoring the
device in position.
5. A device as in claim 1 wherein a thin flange extends from four
sides of the base of the device, the flange at the posterior side
of the device being raised and held in position by extensions of
the vertical walls of said device .[.four sides of the base of
device, the flange at the posterior side of the device being raised
and held in position by extensions of the vertical walls of said
device..].
6. A method for reducing intraocular pressure comprising the steps
of:
creating a scleral flap by making an incision in the sclera
substantially adjacent to the limbus of the eye;
excising a block of sclera by making a second incision into the
sclera underneath the previously produced scleral flap but
extending into the cornea and entering the anterior chamber at
substantially the area where sclera becomes cornea to provide a
pocket in the sclera and a shelf in the cornea .[.and to provide a
window providing direct fluid contact with the anterior chamber of
the eye.].;
.[.providing a device for relieving intraocular pressure, said
device comprising a body portion composed of a biocompatible porous
material, said body portion comprising a first end portion and a
second end portion, said body portion defining pores therethrough,
said pores being of such size and quantity as to permit drainage of
fluid from the anterior chamber to the scleral tissue without
collapse of the anterior chamber.].; and
placing .[.said device for relieving intraocular pressure.].
.Iadd.the hexahedrally shaped device of claim 1 .Iaddend.in said
pocket of the sclera .[.whereby said first end.]. .Iadd.with the
anterior portion of said device .[.is.]. positioned in said shelf
of the cornea .[.such that said first end portion is adjacent said
window and is in direct fluid contact with the anterior chamber
without extending substantially into the anterior chamber and
whereby said second end portion is.]. .Iadd.with the remaining
portions of the device .Iaddend.positioned within the sclera.
.Iadd.
7. A device for relieving intraocular pressure comprising a body
portion constructed of a biocompatible material having flow
passages therein; said flow passages selected from the group
consisting of pores, openings, channels and spaces between fibers
in a meshwork of fibers; said device having a substantially uniform
cross-section adapted to be fitted within the scleral tissue of the
eye at an area adjacent an opening of, with no substantial
extension into, the anterior chamber of the eye at a first position
adjacent to the area of the eye where the sclera makes the
transition into clear cornea of the eye; and extending to a second
position within the scleral tissue of the eye, the distance between
said first and second positions defining the length of the body
portion through which fluid can flow, said length being
approximately six (6) millimeters; said flow passages being of such
size and quantity as to permit drainage of fluid from the anterior
chamber to the scleral tissue without collapse of the anterior
chamber..Iaddend..Iadd.8. A method for reducing intraocular
pressure within the anterior chamber of an eye, said method
comprising the following steps
a. creating a scleral flap by making an incision in the sclera of
the eye substantially adjacent to the limbus of the eye;
b. excising a block of scleral tissue by making a second incision
into the sclera underneath the previously produced scleral flap but
extending into the cornea and entering the anterior chamber at
substantially the area where sclera becomes cornea to provide a
pocket in the sclera and a shelf in the cornea, c. placing a device
for relieving intraocular pressure, said device comprising a body
portion constructed of a biocompatible material; and having flow
passages therein; said device having a first end portion and a
second end portion with said flow passages therebetween; and
d. the device being placed in said pocket of the sclera with said
first end portion of said device positioned in said shelf of the
cornea whereby said first end portion of said body portion is in
direct fluid contact with the anterior chamber of the eye without
substantial extension into the anterior chamber of the eye and with
the second end portion of said device positioned within the sclera
of the eye to permit drainage of fluid from the anterior chamber
into the scleral tissue without collapse of the anterior
chamber..Iaddend.
Description
FIELD OF INVENTION
This invention relates to the drainage of aqueous humour from eyes
in the course of relieving eye disorders. Specifically, the
invention relates to an implant which, when permanently affixed to
or implanted in a specific area of the eye, will provide such
drainage efficiently, for longer periods than heretofore
accomplished, and, in short, will provide relief and prevent (or at
least postpone) the adverse ultimate effects of glaucoma.
BACKGROUND OF THE INVENTION
The eyeball is composed of three basic layers: (1) the sclera. (2)
the middle layer and (3) the retina.
The sclera is the outer layer of the eyeball. It consists of tough,
white tissue that serves as the supporting framework of the eye. At
the front of the eye, the sclera is continuous with the clear,
transparent cornea through which light enters the eye. Behind the
cornea is a small space, the anterior chamber, which contains a
clear watery fluid called the aqueous humour.
The middle layer is composed of three parts: (1) the choroid. (2)
the ciliary muscle, and (3) the iris. The choroid lies behind and
to the sides of the eyeball making up about 80% of the middle
layer. It contains most of the blood vessels that nourish the
eye.
Toward the front of the eyeball, the choroid becomes the ciliary
muscle. This muscle is connected by fibers to the lens, keeping the
lens in place and controlling its shape.
At the very front, the middle layer becomes the iris, a thin
curtain of tissue in front of the lens. A round opening in the
iris, whose size is controlled by muscles in the iris, is called
the pupil.
In simple terms, the cornea refracts light through the anterior
chamber and then through the pupil, the entrance aperture of the
eye to the lens. The lens serves to focus the refracted light
through the vitreous chamber containing the vitreous humour onto
the retina, the rear surface of the eye.
Normally the fluid within the eye, the aqueous humour, is produced
by the-ciliary body and migrates through the pupil into the
anterior chamber, the small space behind the cornea. From this
chamber, the liquid migrates through the trabecular meshwork and
into the aqueous veins which form fluid collection channels beneath
the conjuctiva, the latter covering the front of the eyeball except
for the cornea.
When the aqueous, migration, described above, is insufficient to
relieve the build-up of intra-ocular pressure, glaucoma results.
This pressure build-up is usually due to one or more obstructions
in the trabecular meshwork. Unless controlled, the high pressures
associated with glaucoma ultimately leads to permanent damage of
the optic nerve, the nerve formed from the sensitive fibers of the
retina.
The object of the present invention is to provide a device that can
be implanted permanently, simply and effectively to permit
substantially normal migration of fluid out of the anterior chamber
of the eye and, thus, avoid the abnormal build-up of intra-ocular
pressure. Another object is to provide the implant in a manner that
will also avoid excessive migration of fluid that would lead to
collapse of the anterior chamber with its accompanying
complications.
PRIOR ART
U.S. Pat. No. 4,457,757, issued Jul. 3, 1984 to A. C. B. Molteno,
involves the use of at least two ridged bodies anchored to the
sclera with two tubular extensions, one communicating through the
sclera to the anterior chamber to drain the aqueous humour out of
the eyeball.
U.S. Pat. No. 4,750,901, issued Jun. 14, 1988, to A. C. B. Molteno,
recognized a problem that arose with his earlier device (as
described in U.S. Pat. No. 4,457,757). In the first few days after
insertion of the earlier device, the pressure within the eye tends
to fall to an unacceptably low level "which may result in surgical
complications which damage sight". This fall in pressure is due to
excessive absorption of the aqueous humour by the patient's Tenon
capsule, a smooth layer of tissue that covers the scleral plate
when it is sutured to the eye. This later patent discloses the use
of a subsidiary ridge in the upper surface the scleral plate that
provides, with a portion of the Tenon's tissue, a small cavity
where aqueous humour is drained initially and, thus, the aqueous
humour can only be partially absorbed by the small area of Tenon's
tissue exposed.
U.S. Pat. No. 4,634,418, issued Jan. 6, 1987, to P. S. Binder,
involves the implantation of a seton constructed of a hydrogel in
the anterior chamber of the eye to alleviate intra-ocular pressure.
Once implanted, the seton acts as a wick to transfer aqueous humour
from the anterior chamber to the space under the conjunctiva
without allowing bacteria to ingress into the eye. Implantation is
made after the removal of a rectangular-sized piece of cornea,
Schalbe's line and a portion of the trabecular meshwork.
U.S. Pat. No. 4,722,724, issued Feb. 2, 1988, to S. Schocket,
involves the use of an implant that includes two connected tubes or
a tube connected to a band. One tube is located in the anterior
chamber and the other tube or band is located around the orbit of
the eye. To prevent hypotony, a destructible value is located at
the end of the tube inserted with the interior chamber to control
the pressure of the aqueous humour flowing from the chamber.
U.S. Pat. No. 4,787,885, issued Nov. 29, 1988 to P. S. Binder, is a
continuation of an application that was a continuation-in-part of
the application that resulted in U.S. Pat. No. 4,634,418. This
patent, like its predecessor, also involves the removal of a
rectangular-sized piece of cornea, Schwalbe's line and a portion of
the trabecular meshwork to accomodate a seton; and the seton
permits migration of the aqueous humour from the anterior chamber
to the area beneath the conjunctiva (the external covering of the
eye).
In both patents, the inventor achieves fluid flow to the exterior
of the sclera into a space created beneath the conjunctiva and the
accompanying Tenon's tissue that covers the scleral plate, i.e.
outside the main body of the eye. Since these areas are
particularly agressive in healing, the reduction in intra-ocular
pressure is short-lived; the space created beneath the conjunctiva
and the tenon tissue tends to collapse and prevent further
migration of the fluid from the anterior chamber with the
consequent pressure increase, characteristic of glaucoma.
The object of the present invention is to provide a means and
method for treating the excessive intra-ocular pressure
characteristic of glaucoma in a manner which will not be defeated
by the subsequent healing process i.e. in a manner that will
provide the patient with relief for several years. A further object
is to help avoid other problems such as collapse of the anterior
chamber, penetration of scar tissue over the trabecular meshwork,
which tend to occur in the immediate post operative period with the
conventional glaucoma surgery (trabeculotomy) disclosed in the
prior art.
SUMMARY OF THE INVENTION
The invention involves an implant that is biocompatible with the
tissue of the eye and allows fluid to migrate from the anterior
chamber into the coarsely woven fibers of the sclera, thus
by-passing the obstructed trabecular meshwork but, instead of
leaving the body of the eye, exiting into the outer layer of the
eyeball, the sclera. The normal pressure of fluid in the sclera
serves to control the flow from the anterior chamber in a way that
disastrous collapse of the chamber is prevented. Further, by not
creating a space to accept fluid beneath the conjunctiva and the
associated Tenon's tissue, the aggressive healing of these areas is
not effective in recreating the excessive intra-ocular pressure in
the anterior chamber.
Basically, this invention involves substituting a material that is
composed of small pores of similar size or larger than a healthy
trabecular meshwork in an area almost adjacent to the area of the
troubled trabecular meshwork, i.e. close to where the sclera meets
the cornea. In this manner, an area of relatively small pores
within the implant, is placed within the relatively large pores of
the sclera.
Specifically, the device for relieving intraocular pressure
comprises a body portion and wall portions in substantially
hexahedral form; at least the body portion is composed of a
biocompatible porous hydrogel material. The device is adapted to be
implanted within the scleral tissue of the eye with at least one
edge of the device at an opening of, with no substantial extension
into the anterior chamber adjacent to the area where the sclera
makes the transition into the clear cornea of the eye. The pores of
the body portion are of such size and quantity as to permit
drainage of fluid from the anterior chamber to the scleral tissue
without collapse of the anterior chamber. The wall portions have at
least one extension on at least one wall portion for anchoring the
device securely in position.
The implant is made from a hydrogel or other material which is
biocompatible with the tissue of the eye. Such hydrogel material
may have a water content ranging anywhere from about 30% to about
80%. Typically, such materials comprise silicones, acrylic polymers
and/or fluorocarbon polymers or the like. The implant is shaped to
retain its position once it is implanted within the eye and to
provide sufficient surface area to accomodate the migration of the
aqueou humour in a controlled manner, i.e. enough migration to
reduce intra-ocular pressure but not enough to cause collapse of
the chamber.
The invention will be more clearly understood by referring to the
drawings and the description which follow.
THE DRAWINGS
FIG. 1 is a cross-sectional view of the eye showing one embodiment
of the invention implanted therein;
FIG. 2 is a side view of that embodiment of the invention;
FIG. 3 is a front view of that embodiment;
FIG. 4 is a plan or top view of that emobodiment;
FIG. 5 is a side view of another emobodiment of the invention;
FIG. 6 is a front view of that other embodiment; and
FIG. 7 is a plan view of that other embodiment.
DETAILED DESCRIPTION OF THE INVENTION
In the first embodiment, the overall shape of the device 11 is a
hexahedral structure having a substantially rectangular
cross-section as shown in FIG. 1, approximately 6 mm in length, 3
mm in width, and 1/2 mm in depth. The device 11 is designed to be
placed in a pocket made in the sclera 12 as seen in FIG. 1 in the
following manner. An incision is made in the sclera, 2 mm from the
limbus of the eye. A rectangular flap is raised into the clear
cornea 13. The overall thickness of this flap is approximately 1/3
mm. Following the same incision technique, another flap of sclera
12 is raised underneath the previously made flap but extending into
clear cornea 13. This block of sclera is then excised by entering
the anterior chamber 14 at the anterior wound edge 15 (just as the
sclera 12 makes the transition into clear cornea, 13). The aqueous
fluid would then be able to enter this space through an opening;
16, 4 1/2 mm in length, 1 mm in width, and 1/2 mm in depth. (Since
the cornea follows a curve, the tissue excised would be triangular
when viewed from the side.)
The implant 11 is then placed in this pocket created in the sclera
12 with the anterior portion of the device anchored in the lamellar
shelf 17 previously created in the clear cornea 13. It should be
noted that by anchoring the device in the lamellar shelf rather
than extending the device into the anterior chamber, contact with
the endothelial cells 18 along the interior surface of the cornea
is avoided. Such contact would result in the death of these cells
and the loss of corneal function.
Small lamellar dissections (1 mm in size) are created in the
posterior wall, medial wall and lateral wall of the sclera 12.
Using the embodiment of the device containing flanges, the flanges
19 (or extensions integral with the device) are placed within these
lamellar dissections. By sliding the device 11 anteriorly, it
becomes firmly anchored in the previously prepared corneal lamellar
shelf 17. If necessary, it can be further secured by suturing the
device to assure maintenance of its position. The first scleral
flap is then sutured back into position. The sclera 12 with the
implant 11 in position would be of approximately the same thickness
as before the procedure.
Fluid would then exit the anterior chamber 14 through the incision
under the flap and to the implanted device 11. It would then enter
the implant 11 which would allow it access to three vertical walls
of sclera because of the porous nature of the interior 20 of the
implant. The coarsely woven fibers of the vertically cut sclera 12
would then allow the fluid to exit into the tissue 21 of the sclera
12.
The other embodiment shown in FIGS. 5, 6 and 7 consists of a
similar basic implant 11 having similar dimensions but with a thin
flange 19 (1/8 mm) around the base of the implant on all four
sides. The flange would project 1 mm from the sides that would be
in contact with the sclera only and about 1/2 mm for the side which
would project into a raised flange. This raised flange is attached
by a 1 mm extension 22 of the vertical walls of the portion of the
implant in contact with the sclera. This extension is approximately
1/8 mm thick. Attached perpendicularly to this extension is the
flange 19. The point of attachment is at the mid section of the
flange. The flange is 1/8 mm thick and 2 mm wide. The posterior
section is 7 mm in length and the two sides are 2 1/2 mm in
length.
This embodiment is implanted in a similar fashion to the previously
described implant with the following modifications. 1. The initial
scleral flap would be 1/2 mm. 2. A block of sclera would not be
excised. 3. A lamellar dissection would be performed at the base of
the flap for approximately 1 mm. 4. After the opening into the
anterior chamber is created, the implant is placed into position
sliding the posterior flange into the previously formed space from
the lamellar dissection. The scleral flap is then placed back into
its previous position and underneath the superior flange. This
superior flange would overlie the incision into the sclera to
create a flap of 1 mm on each side except for the furthermost
anterior aspect (which would not be covered by Tenon's tissue since
it does not insert as far anteriorly as the conjunctiva). The
scleral flap is then sutured into position through the superior
flange.
This embodiment would help prevent ingrowth of Tenon's tissue into
the incision and would be firmly anchored into position. It also
would allow access to vertically cut edges of sclera in the same
manner as the previous embodiment.
A further modification of the device of the invention involves the
particular method by which the fluid from the anterior chamber
travels to the sclera. This modification would involve the use of a
meshwork of fibers .Iadd.26 .Iaddend.to allow rapid flow of fluid
through the spaces .Iadd.28 .Iaddend.between the fibers. The
meshwork of fibers .Iadd.26 .Iaddend.being made of a biocompatible
material would be flexible. The meshwork would allow fluid flow to
the vertically cut edges of the implant and the sclera.
Another way to achieve porosity would be through a system of
channels .Iadd.30 .Iaddend.through the implant. A variety of
patterns could be cut so as to achieve high fluid flow through the
implant to the vertically cut edges. For example, a fan shaped
system .Iadd.32 .Iaddend.of drilled holes or a grid pattern of
drilled holes from front to back or an interlocking pattern drilled
from side to side, etc. could be used. The purpose and design are
such that fluid could pass through, as described above, and the
implant would resist collapse from the imposed pressure.
A typical operation for inserting the preferred embodiment of the
invention follows: After retrobulbar anesthesia, the superior
rectus muscle is placed on a four O silk bridal suture. Following
this, a conjunctival flap is raised starting at the superior rectus
and working forward to This is then reflected back to the cornea.
Cautery is used to obtain hemostasis and to outline the location of
the placement for the implant. A rectangular area, 5 mm by 3 mm, is
outlined using a 64 Beaver blade. A small groove is made on the
sclera side to half the depth of the sclera. This is grasped at one
corner and the flap is dissected anteriorly until the rectangular
flap is completely raised in the clear cornea. At this point a 75
blade is used to make a stab incision into the anterior chamber of
the eye and a 1 by 4 mm section of the cornea and trabecular
meshwork are excised en bloc.
Using a lamellar dissecting blade, attention is turned to the
posterior aspect of the bed of the rectangular flap. Further
dissection at the base is carried posteriorly for approximately 0.5
millimeter. The implant is then placed into position in this bed
with the inferior posterior flap laid into the groove that has just
been created on the posterior aspect of the bed. The anterior
portion is in direct communication with the anterior chamber. The
scleral flap is then laid over this implant and tucked in
underneath the superior flanges that are present. If necessary, a
portion of the scleral flap can be excised so that the sclera lays
down smoothly over the implant. The implant is then sutured to the
sclera on both sides with a 10-O nylon suture through the fixation
holes in the superior flange. The conjunctival tissue is then
sutured back together with a 6-O-plain gut running suture.
* * * * *