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Claims  |
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What I claim is:
1. A method for opposing deformity, displacement, and expulsion of ocular
tissues during eye surgery of the types in which a cut is present through
the ocular wall comprising the steps of:
(a) generating an air pressure higher than ambient atmospheric pressure in
a space outside the eye that bears upon a designated surgical field;
(b) concurrent with step (a), maintaining those surfaces of the eye that
lie outside the border of said designated surgical field at ambient
atmospheric pressure;
(c) concurrent with steps (a) and (b), stabilizing the eye against the
applied pressure; and
(d) concurrent with steps (a), (b), and (c), providing access of the
surgeon to the designated surgical field.
2. The method of claim 1 wherein step (a) of generating an air pressure
higher than ambient atmospheric pressure is comprised of the steps of:
(e) assembling an air chamber having an aperture whose edges are coupled to
the eye along the border of the designated surgical field; and
(f) generating an air pressure higher than atmospheric in the chamber.
3. The method of claim 2 wherein the coupling of the chamber aperture to
the eye is achieved by means of suturing.
4. The method of claim 2 wherein step (b) of maintaining those surfaces of
the eye that lie outside the border of the designated surgical field at
ambient atmospheric pressure is comprised of the steps of:
(g) restraining any part of the chamber that might directly or indirectly
bear upon those surfaces of the eye outside the border of said designated
surgical field using chamber restraints; and
(h) restraining the head of the patient from movement that might compress
the eye against said chamber or said chamber restraints.
5. The method of claim 3 wherein step (c) of stabilizing the eye against
the applied pressure consists of the step of:
(j) stabilizing the eye along the border of said designated surgical field.
6. The method of claim 5 wherein step (d) of providing access of the
surgeon to the designated surgical field is comprised of:
(k) providing portals in the air chamber through which the hands of the
surgeons or instruments may pass into the chamber and remain during
surgery without causing substantial pressure change from the desired
pressure level as a result of leakage between the portal and the object
passing through it;
(l) providing airlocks for the exchange of surgical instruments and
materials into and out of the chamber if and when required by the surgical
procedure to be done; and
(m) providing transparency for enough of the chamber walls to permit
observation of the surgery or building observation devices into the
chamber walls.
7. The method of claim 6 wherein step (e) of assembling an air chamber
includes the step of:
(n) attaching a flexible drape to a chamber across an opening in said
chamber so that the flexible drape becomes part of the wall of said
chamber, and with the aperture in said chamber formed in the drape.
8. The method of claim 7 wherein the step of attaching a flexible drape to
said chamber is comprised of the step of:
(o) clamping the flexible drape using clamp means that compress the drape
against a rigid portion of said chamber.
9. The method of claim 8 with the aperture of the chamber preformed in the
flexible drape.
10. The method of claim 8 with the aperture preformed in a flexible
adhesive patch, and further comprising the steps of:
(p) cutting a hole in the flexible drape smaller than the size of the
adhesive patch, but larger than the size of the patch aperture; and
(q) applying the adhesive patch to the flexible drape over the hole in the
drape so that the aperture of the patch, in effect, replaces the hole in
the drape.
11. The method of claim 7 wherein step (g) is carried out by the flexible
drape under pressure being restrained from bearing upon surfaces of the
eye outside the border of the designated surgical field by the natural
support effect of the bony structures of the patient's face.
12. The method of claim 7 wherein step (g) is carried out by the flexible
drape under pressure being restrained from bearing upon the surfaces of
the eye outside the border of the designated surgical field by the natural
support effect of the bony structures of the patient's face and by
appliances attached to the patient's face to alter the effective
supportive contour of the patient's face.
13. The method of claim 12 further comprised of an adhesive undersurface on
the drape and appliances to stabilize their position.
14. The method of claim 7 wherein step (g) is carried out by the flexible
drape under pressure being restrained from bearing upon the surfaces of
the eye outside the border of the designated surgical field by the natural
support effect of the bony structure of the patient's face and the
attachment of the drape to rigid parts of said chamber whose position is
fixed relative to a rigid plate to which the patient's head is
immobilized.
15. The method of claim 7 wherein step (g) is carried out by the step of:
(r) adjusting the position and immobilizing the position of rigid
protective structures between the surfaces of the eye outside the border
of the designated surgical field and the flexible drape, to act as a
shield for the eye against movement of the flexible drape under pressure.
16. The method of claim 7 wherein step (j), of stabilizing the eye along
the border of the designated surgical field, is carried out by the
flexible drape and its aperture whose edges are coupled to the eye along
the border of the designated surgical field being supported by the natural
support effect of the bony structures of the patient's face.
17. The method of claim 7 wherein step (j), of stabilizing the eye along
the border of the designated surgical field, is carried out by the
flexible drape and its aperture whose edges are coupled to the eye along
the border of the designated surgical field being supported by the natural
support effect of the bony structures of the patient's face and by
appliances attached to the patient's face to alter the effective
supportive contour of the patient's face.
18. The method of claim 17 further comprised of an adhesive undersurface on
the drape and appliances to stabilize their position.
19. The method of claim 7 wherein step (j), of stabilizing the eye along
the border of the designated surgical field, is carried out by the
flexible drape and its aperture whose edges are coupled to the eye along
the border of the designated surgical field being supported by the natural
support effect of the bony structures of the patient's face and the
attachment of the drape to rigid parts of said chamber whose position is
fixed relative to a rigid plate to which the patient's head is
immobilized.
20. The method of claim 7 wherein step (j) is carried out by the steps of:
(s) coupling to the eye along the border of the designated surgical field a
rigid closed loop contoured to lie against the eye along the border of the
designated surgical field;
(t) coupling the edges of the chamber aperture to the rigid closed loop;
and
(u) stabilizing the position of the rigid loop on the eye using a rigid but
adjustable support structure connecting the rigid loop to a rigid part of
said chamber that is in fixed relation to a rigid plate to which the head
is immobilized.
21. The method of claim 20 wherein step (g) is achieved by the addition of
rigid support projections attached to the rigid closed loop of step (s),
these projections passing between the surface of the eye outside the
border of the designated surgical field and the flexible drape, to act as
a shield for the eye against movement of the flexible drape under
pressure.
22. The method of claim 21 wherein the rigid loop is coupled to the eye by
suturing.
23. The method of claim 22 wherein the coupling of the chamber aperture to
the rigid loop is achieved by means of suturing.
24. The method of claim 22 wherein the coupling of the chamber aperture to
the rigid loop is achieved by means of stretching an elastic aperture edge
over the rigid loop so as to fit into a groove in the rigid loop.
25. The method of claim 22 wherein the coupling of the chamber aperture to
the rigid loop is achieved by means of stretching an elastic aperture edge
over the rigid loop so as to fit against a surface of the rigid loop.
26. The method of claim 22 wherein the coupling of the chamber aperture to
the rigid loop is achieved by means of the weight of the drape under
pressure causing the aperture edges to be in application to the surface of
the immobilized loop.
27. The method of claim 7 wherein step (j) is carried out by the steps of:
(s) coupling to the eye along the border of the designated surgical field a
rigid closed loop contoured to lie against the eye along the border of the
designated surgical field;
(t) coupling the edges of the chamber aperture to the rigid closed loop;
and
(u) stabilizing the position of the rigid loop on the eye using a rigid but
adjustable support structure connecting the rigid loop to a rigid plate to
which the head is immobilized.
28. Apparatus for opposing deformity, displacement, and expulsion of ocular
tissures during eye surgery of the types in which a cut is present through
the ocular wall comprised of:
(a) a chamber defining an enclosed air space having an aperture the size of
a designated surgical field of the eye;
(b) coupling means for attaching the aperture edges to the border of the
designated surgical field of the eye;
(c) pressurizing means for controlling the level of air pressure at or
above atmospheric pressure in the enclosed space;
(d) surgical access means for the surgeon, surgical assistants, and
instruments to have access to the designated surgical field so that
surgery can be performed while the enclosed space is pressurized at or
above atmospheric pressure, and for the anesthesiologist to have access to
the patient's airway which lies outside the pressurized space;
(e) eye stabilizing means for supporting the eye against the air pressure
on the designated surgical field;
(f) eye shielding means for preventing said chamber from indenting that
part of the external eye wall lying outside the border of the designated
surgical field; and
(g) head stabilizing means for preventing movement of the patient's head
and eye against said chamber, said coupling means, said eye stabilizing
means, and said eye shielding means.
29. The apparatus of claim 28 wherein the wall of component
(a) is comprised in part of a flexible air resistant drape with said
aperture present in the drape.
30. The apparatus of claim 29 wherein said chamber has rigid parts defining
an opening and a gasket on said rigid parts and said drape is clamped
across said opening in the enclosed air space to said gasket on said rigid
parts.
31. The apparatus of claim 30 wherein said aperture is comprised of a
flexible adhesive patch that is applied over a hole cut in the drape so
that the aperture replaces the hole.
32. The apparatus of claim 31 wherein said aperture has an edge formed of
elastic material.
33. The apparatus of claim 31 wherein said coupling means of component (b)
comprise sutures.
34. The apparatus of claim 33 further comprised of an adhesive undersurface
on the drape.
35. The apparatus of claim 31 wherein said coupling means of component (b)
comprise:
(h) a rigid closed loop contoured to be in contact with the eye wall along
a continuous linear zone of contact that forms a closed loop along the
border of the designated surgical field;
(j) suture means for coupling the rigid loop to the eye; and
(k) means for coupling the aperture edges to the rigid closed loop.
36. The apparatus of claim 35 wherein said means (k) for coupling the
aperture edges to the rigid closed loop are sutures.
37. The apparatus of claim 35 wherein said eye stabilizing means of
component (e) comprise:
(l) said rigid closed loop;
(m) said suture means for coupling said rigid loop to the eye; and
(n) an adjustable rigid support structure fixing the position of the rigid
closed loop in relation to a rigid plate to which the patient's head is
stabilized.
38. The apparatus of claim 37 wherein said eye shielding means of component
(f) include:
(o) rigid projections extending from said rigid closed loop that pass
between the undersurface of said flexible drape and those parts of the
eyeball surface lying outside the border of the designated surgical field;
(p) said rigid closed loop; and
(q) said adjustable support structure.
39. The apparatus of claim 38 wherein said means (k) of coupling the
aperture edges to the rigid closed loop are sutures.
40. The apparatus of claim 38 wherein said means of coupling the aperture
edges to said rigid closed loop include a surface on the immobilized rigid
closed loop to which the aperture edges are apposed by the weight of the
drape under pressure.
41. The apparatus of claim 38 wherein said rigid closed loop has a groove
and said means of coupling the aperture edges to said rigid closed loop
comprise an elastic aperture stretched over the rigid closed loop so as to
fit into said groove in the rigid closed loop.
42. The apparatus of claim 38 wherein said rigid closed loop has a surface
and said means of coupling the aperture edges to said rigid closed loop
comprise an elastic aperture stretched over the rigid closed loop so as to
fit against said surface of the rigid closed loop.
43. The apparatus of claim 38 wherein said means of controlling the
pressure at or above atmospheric of component (c) comprise a variable
speed blower (64), a humidifier (63) and filter (60) connected to said
blower, an inflow hose (28) connecting said filter and entering said
chamber and an outflow hose (72) connecting the chamber to a T-joint (75)
having one end connected to a pressure gauge (74) and another end immersed
in water to a depth approximating the desired pressure in the chamber.
44. The apparatus of claim 38 wherein said means of controlling the
pressure at or above atmospheric of component (c) comprise a source of
compressed air, a humidifier (63) and filter (60) connected to said source
of compressed air, an inflow hose (28) connecting said filter and entering
said chamber and an outflow hose (72) connecting the chamber to a T-joint
(75) having one end connected to a pressure gauge (74) and another end
immersed in water to a depth approximating the desired pressure in the
chamber.
45. The apparatus of claim 44 wherein said surgical access means of
component (d) comprise portals in said chamber walls through which the
surgeons may pass their arms and surgical instruments with hermetic seals
around their arms or instruments, and further comprise transparent walls
through which the surgeons can see the surgical field and walls
incorporating the objective of a surgical microscope.
46. The apparatus of claim 45 wherein said hermetic seals consist of simple
rubber diaphragms bonded across said portals in the chamber walls, the
diaphragms having circular openings whose unstretched size is less than
the size of the arms or instruments passing through them.
47. The apparatus of claim 46 wherein said surgical access means further
comprise a passageway into the enclosed space having a first doorway
opposite said enclosed space and a second doorway to the enclosed space
which can be operated in sequence to permit passage of surgical
instruments or material into and out of the enclosed space without
substantial loss of pressure in the enclosed space.
48. The apparatus of claim 47 wherein said chamber and its supporting
structures include an arch-like part which permits access to the nose and
mouth of the patient.
49. The apparatus of claim 47 wherein said chamber includes a rigid upper
enclosure, said eye shielding means of component (f) include a base frame
(8) resting on a base plate (16), and anchored against lateral motion by
pins protruding upwards from the base plate into holes in the base frame
(14), the base frame (8) having an upwardly directed surface contoured to
match that of a downwardly directed gasketed surface of said rigid upper
enclosure (4) so that when a flexible drape (32) is laid over the base
frame (8) and the upper enclosure (4) emplaced and clamped to the base
plate (16), a pressure chamber is formed over the patient having rigid
parts in fixed relation to the base plate (16) to which the patient's head
is stabilized.
50. The apparatus of claim 49 wherein said head stabilizing means of
component (g) comprises a rigid base plate having a stabilized head rest
and straps and post-mounted head holders to stabilize the head resting on
its head rest to the base plate.
51. The apparatus of claim 29 wherein said chamber has rigid parts defining
an opening and said drape is clamped across said opening in the enclosed
air space to said rigid parts.
52. The apparatus of claim 51 wherein the drape has a reinforced edge or
frame contoured to match the rigid parts of said chamber to which it is
clamped.
53. The apparatus of claim 51 wherein said aperture is preformed in the
drape.
54. The apparatus of claim 29 wherein said flexible air resistant drape is
preformed to conform to facial contours around the eye. |
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Claims |
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Description |
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BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to new and improved methods and apparatus for
opposing deformity, displacement, and expulsion of the ocular tissues
during eye surgery. The method and apparatus are for use during eye
surgical procedures in which an incision is made into an internal
compartment of an eye. Such eye surgical procedures include various types
of corneal, cataract, vitreous, retinal, and glaucoma surgery. The method
and apparatus are also for use during eye surgical procedures to repair an
eye already cut open by traumatic injury. The method and apparatus also
provide a means of regulating pressure within the eye during surgery. The
method and apparatus also provide a means of filtering and humidifying the
air in the vicinity of the open incision. The particular surgical case
must be evaluated to determine whether or not the use of the method and
apparatus is appropriate.
2. Description of the Prior Art
The state of the art of methods and apparatus for performing eye surgery
may be ascertained in large measure by reference to U.S. Pat. Nos.
3,186,308; 3,612,468; 3,868,171; 4,014,342; 4,108,182; 4,184,491;
4,019,514; 4,157,718; 4,041,947; 4,168,707; 4,184,510; 4,184,492;
4,180,074; and 3,572,319; "Vitreous Microsurgery" by Steve Charles
(Williams & Wilkins, Baltimore, 1981); "Surgery of the Eye" by E. D.
Dorrell (Blackwell Scientific Publications, London, 1978); "Cataract
Surgery and Its Complications" by Norman S. Jaffe (C. V. Mosby Company,
St. Louis, 1981); "An Atlas of Ophthalmic Surgery" by John Harry King, Jr.
and Joseph A. C. Wadsworth (J. B. Lippincott Company, Philadelphia, 1981);
"Microsurgery of the Anterior Segment of the Eye" by Richard C. Troutman
(C. V. Mosby Company, St. Louis, Volume I, 1974, Volume II, 1977); and
Weck Optical Product Bulletins, "016 XY Translation Arm (1981)" and "004
XY Translation Table" (Edward Weck & Company, Inc., Box 12600, Research
Triangle Park, N.C. 27709), the disclosures of which are incorporated
herein.
Many surgical procedures are employed to restore, preserve, or improve
vision. Some of these, including cataract surgery and penetrating
keratoplasty (corneal transplantation), require that a surgical incision
be made into the tissues and compartments of the eye. Before such an
incision has been made, an eye with a normal intraocular pressure of about
15 mm Hg. above atmospheric maintains a steady resistance to deforming
forces. Even an eye with an intraocular pressure measuring zero relative
to atmospheric pressure can, before an incision is made into the
intraocular compartments, offer considerable resistance to transiently
applied forces by responding with a transient rise in intraocular
pressure. However, an eye with a cut connecting its internal compartments
with the operating room space at ambient atmospheric pressure has lost
most of its ability to resist deformation because the ocular tissues can
flow out through the opening, unimpeded, as a deforming force is applied.
Various deforming forces bear upon the eye at various times during
surgery. Thus, when a surgical incision is made, there is a tendency for
the eyeball to assume a distorted shape and for fluid and tissue to be
displaced towards the incision and to be expelled from the eyeball through
the incision. The deformation results from the action of gravity on the
tissues and fluids of the eye, from the contraction of the normally
stretched elastic fibers of the ocular wall, from the pull of muscles
fastened to the outside of the eye, and from the effect of compressed
orbital structure. The deformation can also result from the pressure of
surgical instruments laid on the eye or the orbit. Furthermore, when the
surgical incision is made, the pressure within the eye, which, in a normal
eye, is about 15 mm Hg. above atmospheric, falls towards atmospheric
pressure, i.e., towards the ambient pressure in the operating room. This
fall of the intraocular pressure favors seepage or "transudation" of fluid
from the lumens of capillaries in the structures of the eye, through the
capillary walls, and into the tissues and compartments of the eye. The
fall in intraocular pressure also favors the occurrence of intraocular
hemorrhage due to the failure of support for weak points in the walls of
blood vessels of the eye which then rupture. Both transudation and
hemorrhage contribute to internal deformation and loss of tissue or fluid
through the incision. If a choroidal hemorrhage of sufficient magnitude
occurs, the entire contents of the eye, including the retina, can be
rapidly and unavoidably expelled, resulting in loss of the eye. In
general, the greater the ocular deformity taking place during surgery, the
greater the ocular damage, the greater the difficulties encountered by the
surgeon, and the poorer the results of the surgery.
Various methods of dealing with the problems of intraocular hypotension,
anterior (forward) displacement of the contents of the eye towards and
through the incision, and ocular deformity during surgery have been
described.
One such method attempts to maintain the intraocular pressure above
atmospheric pressure by forcing fluid into the eye through a needle or
cannula. As a result of the maintenance of this pressure differential
between the inside of the eye and the air in the operating room while the
eye is cut open, there is a tendency for fluid or tissue to be pushed out
through surgical incisions, be they for the insertion of microsurgical
instruments or for the infusion cannula itself. The size and position of
the various incisions as well as the position of the infusion cannula
influence to a considerable degree the tendency for fluid or tissue to be
extruded. Since it might harm the eye if tissue prolapses, if excessive
leakage prevents pressure maintenance, if excessive leakage requires
excessively high infusion and intraocular flow rates, or if excessive
leakage obscures the surgeon's view, the incisions must be kept small,
plugged, or blocked. Even with small incisions, the possibility that
tissue will prolapse exists, especially during insertion and removal of an
instrument.
In situations where a large incision is necessary, it is sometimes possible
to reduce the blood pressure of the patient so as to reduce the risk of
expulsive hemorrhage or significant transudation. However, manipulation of
the blood pressure may compromise circulation of blood to the brain, the
heart, the kidneys, as well as to the eye itself.
External mechanical support can be provided for the sclera, i.e., the
ocular coat, at a finite number of points by attachment of a Flieringa
ring, a scleral expander, or the like, around an anterior part of the eye.
However, there is little support for the rearward portions of the eye
because such external supports are sewed only to the exposed parts at the
front of the eye. The effect of hemorrhage or transudate can still be to
separate the choroid and the retina from the sclera because of failure of
the external support to provide appositional force between these
structures. Finally, such external skeletal supports may create
undesirable stresses by supporting the sclera at the same time that the
elastic choroid tends to collapse and fall away from it.
Other methods are also employed to reduce anterior displacement by
producing a "soft eye", i.e., an eye which has an intraocular pressure
lower than normal, before the incision is made. Such methods include
compressive ocular massage, intravenous infusion of osmotic agents to draw
water out of the body tissues, and the use of a needle to aspirate liquid
vitreous. These measures reduce the ocular volume thus relieving
compressive forces so that there will be less resulting anterior
displacement of the ocular contents towards the incision when the incision
is finally made. Paralyzing the ocular muscles with drugs such as
intravenous curare is also employed. (Osmotic agents, liquid vitreous
aspiration, and drugs such as curare are sometimes used after the incision
is made.) These softening techniques have side effects and risks which are
well known.
It is an object of this invention to provide the surgeon with a method and
apparatus for maintaining desired anatomical relationships during the
performance of surgery through an open incision of a size appropriate to
the surgical task to be performed.
DEFINITION
By "designated surgical field" is meant a portion of the eyeball surface,
designated by the surgeon in a particular case, through which all
incisions through the eyeball wall are to be made, through which all
traumatic injury cuts through the eyeball wall are present, and through
which all internal manipulations inside the eye are to be performed.
It should be understood that during the attachment of the invention
apparatus to the eye, access to a slightly larger area than the area
designated as the "designated surgical field" will be required.
It should also be understood that in dividing the eyeball surface into an
area constituting the "designated surgical field" and an area outside the
"designated surgical field", for practical purposes, between the two areas
there will be a boundary line, border, or periphery of finite width to
which structures may be attached without significantly encroaching on
either of the two principle areas. For clarity, in the description of the
invention and in the claims, each of the three zones is specifically
referred to when necessary.
SUMMARY OF THE INVENTION
The method and apparatus of this invention oppose deformity, displacement,
and expulsion of the ocular tissues during eye surgery of the types in
which a cut is present through the ocular wall by
(a) generating an air pressure higher than atmospheric pressure in a space
outside the eye that bears upon the designated surgical field;
(b) concurrent with step (a), maintaining those surfaces of the eye that
lie outside the border of the designated surgical field at ambient
atmospheric pressure;
(c) concurrent with steps (a) and (b), stabilizing the eye against the
applied pressure; and
(d) concurrent with steps (a), (b), and (c), providing access of the
surgeon to the designated surgical field.
In a preferred embodiment of the invention, an enclosed air space is
provided with an aperture the edges of which are attached to the eye along
a line that encompasses the site of the surgical incision to be made. By
pressurizing the enclosed space, pressure is maintained in the vicinity of
the proposed incision site, and in the eye after the surgical incision has
been made, but not on the external surfaces of the eye outside the
enclosed space which continue to be at ambient atmospheric pressure. To
this end, with the patient lying face up on an operating room table, with
his head stabilized to an underlying base plate, a pressurizable chamber
is assembled and supported over the patient's face with its rigid parts
deriving support from the base plate. The walls of the chamber consist in
part of flexible material which is draped over the patient's face. The
edges of an aperture in the drape are attached to the eye along the border
of the designated surgical field. In this embodiment, the attachment of
the drape aperture to the eye is by means of a rigid ring sewn to the eye,
the drape aperture edges being sewn to the ring. The position of the ring
is adjusted and immobilized by a suitable support apparatus. The ring and
its support apparatus serve the function of immobilizing the junction of
the eye and the flexible drape. When the chamber is pressurized, the air
pressure within it exerts force against the surface of the eye within the
circle of the sutured ring, i.e., against the designated surgical field.
Normally, pressure against an anteriorly directed surface of the eye would
result in posterior movement of the eye into the orbital fat cushion
behind the eye. The immobilized ring sutured to the eye serves to prevent
such movement. The ring is also equipped with lateral projections passing
between the drape and those surfaces of the eye that lie outside the
circle of the sutured ring. When the chamber is pressurized, the air
within it exerts force against the surfaces of the drape peripheral to the
aperture. However, the ring projections passing beneath the drape insure
that the drape is not forced down against those parts of the eye that lie
outside the circle of the sutured ring. Portals in the chamber walls
permit access of the hands of the surgeons to the designated surgical
field. Hermetic seals from the portal edges to the surgeons' forearms
prevent excessive leakage of air out of the chamber. Airlocks permit
instruments or surgical materials to be passed into and out of the chamber
without substantial loss of pressure. Air inlet and outlet openings are
provided and used for pressure regulation. Parts of the chamber walls are
transparent to permit visual access to the surgical field, and optical
devices can be built into the walls of the chamber for observation
purposes.
The method and apparatus of the invention thus provide for maintenance of
intraocular pressure above atmospheric even when a large incision is used.
The pressure is transmitted across the incision to the interior of the eye
without applying additional pressure to the external surfaces of the eye
outside the border of the designated surgical field. This tends to
maintain the normal shape and volume of the eye against deforming forces
in a manner that mimics the natural state of the eye. There is an
appositional force between the vitreous, the retina, the choroid, and the
sclera. The pressure maintained within the eye opposes transudation and
hemorrhage. All of the above tends to keep the ocular tissues in their
normal anatomic positions and to prevent displacement of the ocular
contents towards and through the incision.
The invention contrasts with those methods discussed previously which
"soften" the eye before surgery, all of which fail to oppose transudation
and hemorrhage, and most of which deform the eye. As stated previously,
the side effects and risks of the known procedures are well known and, in
many patients, contraindicate their use.
The invention contrasts with those methods discussed previously which
attempt to maintain ocular shape and volume by sewing a relatively rigid
system of interconnecting rings or wires to the outside of the eye at a
finite number of points on the exposed anterior surfaces of the eye.
Though often of considerable benefit, such "exoskeletons" do not support
the eye posteriorly, do not provide appositional forces between retina,
choroid, and sclera, and do not oppose transudation and hemorrhage.
The invention contrasts with pharmacologic lowering of blood pressure as a
means of reducing hemorrhage and transudation because the invention
produces its effect by correcting the causative abnormality, namely,
intraocular hypotension, rather than by introducing a possibly dangerous
compensatory abnormality.
The invention contrasts with the hypothetical use of a hyperbaric chamber
that might encompass the entire head of the patient. While such a chamber
would increase pressure on the ocular tissues and might oppose
transudation and hemorrhage, it would fail to support the natural shape
and volume of the eye because it would not retain the pressure
differential between the inside of the eye and the external surfaces of
the eye. The invention achieves such a differential pressure between the
inside of the eye and all those external ocular surfaces lying outside the
border of the designated surgical field. Thus, unlike the hypothetical
hyperbaric chamber just mentioned, the invention tends to support the
natural shape and volume of the eye.
The invention also contrasts with methods previously employed to maintain
intraocular pressure above atmospheric. As stated previously, with these
other methods, the pressure elevation is effected by a cannula introduced
into the eye, leaving the pressure outside the eye in the vicinity of the
incision at atmospheric. This results in a requirement that the incision
be kept small, reduced in size, plugged, or otherwise blocked, and also
results in a tendency for tissue to prolapse, in spite of the small
incision size, especially during insertion and removal of instruments.
Unlike these other methods, this invention does not generate a difference
in pressure across the incision which is higher inside the eye than
outside because the primary elevation in pressure is generated in a work
space outside the eye in the vicinity of the incision, and is transmitted
secondarily to the inside of the eye via the incision. Since the invention
does not generate a pressure differential across the incision higher
inside the eye than outside, it does not create a tendency for tissue to
prolapse and does not require a small incision. The invention enables the
surgeon to maintain intraocular pressure during those procedures in which
a large incision is either necessary or desirable as well as in those in
which small incisions are used. In addition, the invention can be used to
great advantage in repairing traumatic wounds of the eye, large or small,
by aiding in restoring and maintaining normal anatomic relationships
during the repair. The need to properly place and monitor the position of
pressure cannulas lest they damage the eye during the su | | |
