Note: Descriptions are shown in the official language in which they were submitted.
10685'72
This application relates to an improvement in the control of fluid
flow in a surgical device. More particularly this invention relates to an
improvement in the fluid flow systems for a surgical device useful in catar-
act removal such as that shown by U.S. Patent No. 3,589,363 issued June 29,
1971 to A. Banko and C.D. Kelman for a Material Removal Apparatus and Method
Employing High Frequency Vibrations. The aforesaid patent describes an in-
strument for breaking apart and removing unwanted tissue and material espec-
ially a cataract located in the anterior chamber of the eye by ultrasonically
fragmenting the cataract while simultaneously introducing fluid into the eye
chamber, and withdrawing the fluid and fragmented cataract particles. Briefly
the device described includes a handpiece having an operative tip vibrating
in the ultrasonic range which is also hollow and is in turn surrounded by a
tubular sleeve. In operation the tip of the handpiece including the surround-
ing tubular sleeve are inserted into the anterior chamber of the eye. Treat-
ment fluid is introduced through the hollow sleeve at a constant low pressure.
This introduction of fluid which is called irrigation is to provide a replace-
ment for fluid withdrawn or lost from the eye chamber. The withdrawal of
fluid and suspended material from the anterior chamber is specifically called
aspiration and ideally there is no change in fluid content or anterior cham-
ber pressure as a result of irrigation-aspiration. This of course is impos-
sible to achieve since aspiration is intended to remove solids which until
broken up sometimes tend to occlude or block the fluid withdrawal openings of
the handpiece. ~ -
This problem with control of fluid content and pressure within the
an~erior chamber of the eye during irrigation-aspiration is discussed in de-
tail in U.S. Patent No. 3,696,613 issued September 26, 1972 to Charles Kel-
man for a Surgical Handpiece and Flow Control System for Use Therewith, and
commonly assigned herewith.
A handpiece described in the aforesaid U.S. Patent as well as the
instrumentation described in U.S. Patent No. 3,589,363 provides a tool tip
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insertable in the anterior chamber of the eye with an annular nozzle for
supply of fluid for irrigation, a hollow tool tip which is vibrated at about
40,000 cps to provide the energy to break up the cataract and allow fluid
withdrawal for aspirating the reduced particles and fluid. When the hand-
piece is inserted into the eye, it is extremely important to maintain the
fluid pressure of the chamber within a certain range and to prevent rapid
fluctuations of the pressure and fluid content of the chamber. A collapse of
the anterior chamber for lack of sufficient pressure could result in damage
to soft tissues of the eye as well as possible damage of the eye posterior
capsule itself from contact of the tissues with the vibrating tool tip. This
problem of maintaining the proper pressure is a particularly difficult and
sensitive one and is one of the problems which the apparatus shown in the
aforesaid U.S. Patent No. 3,696,613 was designed to solve. The system shown
therein while satisfactory is quite obviously a rather complex apparatus
which re~uires in terms of control, close and competent operation personnel.
Thus as part of the operation to remove a cataract from the anterior chamber
` of the eye the handpiece is inserted into the chamber through a small incis-
ion and the fluid flow adjusted to the desired level principally by the height
at which the irrigation fluid source is supported to provide a gravity flow
into the eye, and the speed of a constant flow positive displacement pump
in the piping from the eye to withdraw the aspirating stream. The surgeon
then moves the cataract lens into the anterior chamber, applies the ultrasonic
vibration to the tip of the handpiece in contact with the lens and proceeds
- to break up the lens.
As part of the application of the tip to the lens the opening in
` the tip through which aspiration proceeds is periodically occluded by lens
material. During such occlusion, fluid is prevented from entering the hollow
tip, although the constant flow pump continues to operate. The pump oper-
ation thus starts drawing a vacuum in the conduit between the handpiece tip
and the pump. At the same time, the pressure from the gravity feed of irrig-
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ation fluid into the eye remains constant and increases flu;d pressure in the
anterior chamber of the eye, expanding it sormewhat. However once the open-
ing into the handpiece tip is uncapped by fragmentation of the occlusion,
the high vacuum existing in the aspirating system tends to quickly withdraw
fluid from the anterior chamber. This may rapidly decompress the anterior
chamber and draw the enclosing tissues towards the handpiece tip. Besides
the danger represented by the ultrasonic vibrations of the handpiece tip on
contact with these tissues, the rapid decompression itself may be injurious
to the tissues. The apparatus shown by the aforesaid U.S. Patent No.
3,696,613 of course is designed to eliminate such perturbations to the eye
by monitoring and controlling flow. It would be advantageous to have a
system which is not only fail-safe by means of being simple rather than
complex, but is also more easily regulated and controlled by normal operative
personnel rather than trained technicians.
Accordingly the system of the invention consists of a fluid flow
system for use in aspiration of a fluid from a small, pressure-responsive,
fluid containing chamber such as the anterior chamber of an eye, said system
comprising: fluid withdrawal duct means for aspirating said fluid from said
chamber at a rate which avoids rapid pressure changes in said chamber;
aspiration suction means for providing said fluid aspiration in said fluid
withdrawal duct means; and pressure responsive valve means connecting said
fluid withdrawal duct means to said aspiration suction means and responsive
~ directly to the pressure in said fluid withdrawal duct means for opening to
-~ atmosphere when excessive vacuum which would cause said rapid pressure
changes in said chamber, and consequent excessive pressure transients therein,
build-ups in said fluid withdrawal duct means.
A preferred system according to the invention comprises: a fluid
source under substantially constant pressure; fluid inflow means connected
; to the fluid source for limiting flow of the fluid from the source into the
chamber thereby providing irrigation fluid at a predetermined limited flow
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rate and pressure into the chamber; fluid withdrawal means in fluid commun-
ication with the chamber for aspirating fluid from the chamber at a rate to
eliminate transient pressure shocks to the chamber; a constant flow pump
connected to the other end of the fluid withdrawal means, with the pump act-
ing to draw fluid from the chamber through the withdrawal means; and the
withdrawal means including a pressure differential relief valve intermediate
the chamber and the pump, the relief valve responsively opening at a predet-
ermined pressure differential which in combination with the parameters of
the fluid withdrawal means limits the occurrence of pressure transients com-
municated to the chamber, whereby flow resistivity of the withdrawal means
between the chamber and the valve attenuates the pressure changes transmitted
to the chamber when the valve opens in response to the predetermined pressure
; differential between atmosphere and the pressure in the withdrawal means
reaching the predetermined differential pressure.
Preferably where the enclosed volume is the anterior chamber of the
0ye, the relief valve opens to atmosphere in response to a pressure differen-
tial o from 10 mm of mercury (Hg) to 100 mm Hg; the pressure of the fluid
source is in the range of from 10 to lO0 mm Hg; the flow resistivity of the
inflow means is from 0.042 to 18.5 mm Hg per ml per min; the flow resistivity
of the fluid withdrawal means is from 0.35 to 21.5 mm Hg per ml per min; and
; the constant flow volume of the pump is from 5 to 50 ml per min. More part-
icularly the preferred pressure, flow and flow resistivity ranges of the sys-
tem according to the present invention comprise the following: a fluid source
exerting a constant pressure of from 30 to 60 mm Hg; the inflow means having
a flow resistivity of from 0.5 to 2.5 mm Hg. ml per min between the fluid
source at one end and to the operative volume of the anterior chamber of an
- eye at the other end; the fluid withdrawal means having a flow resistivity of
from 1.33 to 3.0 mm Hg. per ml per min. from the operative volume of the ant-
erior chamber of the eye and to the atmosphere; the constant volume pump hav-
ing a flow rate of from 20 to 30 ml per min; and the relief valve connected
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to the flow withdrawal means intermediate the pump and the eye chamber res-
ponsively opening the atmosphere at a pressure differential of between about
30 and 50 mm Hg.
It is therefore an object of this invention to provide a fluidic
control system for use in aspirating a small elastic volumetric space.
Another object of the present invention is to provide an effective
flow control system for aspirating the anterior chamber of the eye.
Yet another object of the present invention is to provide a flow ;~
control system for effectively limiting the transient pressure and flow changes
as felt by the anterior chamber of the eye during irrigation and aspiration
thereof.
Other objects and advantages of the system according to the present
invention will be apparent from the brief description of the drawings and
the preferred embodiment which follows.
Pigure 1 of the drawings is a diagram of the fluidic flow control
system of the present invention; and
Figure 2 of the drawings is an electrical circuit analog of the
flow control system of Figure 1.
In the U.S. Patent No. 3,589,363 described hereinbefore, apparatus
and method for the removal of material by employing high frequency vibration
is shown and described. Briefly the aforesaid patent describes an instru-
ment for breaking apart and removing unwanted material such as for surgically
- removing a cataract from the eye. The apparatus includes a handpiece having
an operative tip vibrating at a frequency in the ultrasonic range ~preferably
about 40,000 cps) with an amplitude controllable up to several thousandths -
of an inch. The operative tip is itself hollow and is in turn surrounded
by a tubular slePve forming an annular passage. The inflow fluid for irrig-
ating the anterior chamber of the eye is introduced into the chamber through
the annular passage and the broken up material, small particles and fluid in
the eye, is with~rawn at the same time through the hollow tip to aspirate
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the chamber.
Referring now to Figure l of the drawings wherein a simplified
diagram of a handpiece 12 is shown with an operative tip 14 having a hollow
withdrawal means 16, and an annular passage 18 surrounding the tip 14 for
introducing fluid into an anterior chamber 20 of an eye undergoing cataract -
surgery.
A more detailed description of the handpiece 12 described above is
provided in the aforesaid United States Patents No. 3,589,363 and
3,696,613 commonly assigned to the assignee herein.
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:
Irriga~ion fluid is introduced into the handpiece 12 via an inflow
hose 22 which is connected at one end to the handpiece and at the other end
to an administration set 23, that is a hose connected to an irrigation fluid
supply bottle 24 suspended by an appropriate bracket tnot shown) a fixed
height 'h' over the level of the handpiece and eye. The fixed height 'h' at
which the fluid supply bottle is suspended acts to apply a fixed fluid pres-
sure to fluid entering the hose 22 from the bottle to the eye. The selected
height is such as to apply a pressure of from about 10 mm Hg to about 100 mm
Hg to fluid entering the administration set and thereby furnish a fluid
source having a constant preselected pressure level in relation to the hand-
piece
More preferably the height at which the supply bottle is suspended
is such as to apply a pressure head of from 30 mm ~g to 60 mm ~Ig. According
to the present invention, this is the sole means for supplying the pressure
head which forces the flow of fluid from the bottle through the administra-
tion set 23, the inflow hose 22 and the annular passage of the handpiece
into the anterior chamber of the eye.
For purposes of this invention the pressure which is internally
applied to the eye is of prime importance. For instance, as described in
United States Patent No. 3,696,613, it is very important that pressure of
the anterior chamber of the eye be maintained within a certsin range of
values to prevent damage thereto. A collapse of the anterior chamber due
to reduced pressure could result in either the iris, the endothelium layer
of the cornea, or the posterior capsule as well as other soft tissue, coming
in contact with the operating tip of the handpiece. This problem of main-
taining the proper pressure is a particularly difficult and sensitive one in
the case of an operative site such as the anterior chamber, which is con-
siderably smaller in volume than the volume of fluid necessary for continu-
ous irrigation and aspiration. The anterior chamber of the eye is, of
course, in the same pressure related system as the apparatus of this inven-
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tion. In a cataract operation, pressure transients are periodically being
induced at the tip of the handpiece due to the presence of a particle or
part: of the cataract. This initially prevents entry of aspirating fluid into
the tip with resulting buildup of suction in the tip, and then sudden clear-
ance of the occlusion blocking the handpiece tip. The apparatus shown in
the United States Patent No. 3~696,613 is designed to reduce and overcome
this problem and as such as effective though expensive and complicated.
Basically the present invention provides an irrigation system
which limits the fluid pressure to which the anterior chamber of the eye is
subject by limiting the height at which the irrigation fluid supply is main-
tained in reference to the eye, and by further limiting the flow rate into
the eye utilizing specified inflow means having a specified resistivity to
flow, as well as relating the irrigation system to the fluid withdrawal or
aspiration system. That portion of the fluidic system co~prising the fluid
withdrawal mesns, the constant flow pump ant the differential pressure relief
valve act in combination to limit fluid flow from the eye, and more import-
antly p~event sudden pressure changes or pressure transients from occuring -~
by increasing the time period over which the pressure changes occur and by
limiting the maximum pressure drop to which the eye would be exposed. This
is accomplished by controlling the constant flow rate of the pump; by setting
a predetermined limit to the pressure differential, the relief valve will
open to atmosphere; and by controlling the flow resistivity of the fluid
withdrawal piping as herein described.
Referring back to Figure 1 of the drawing the operative tip 14 of
the handpiece is hollow and has an internal fluid withdrawal passage 30 con-
stituting part of the fluid withdrawal system of the present invention util-
ized in aspirating the operative site of the eye. A fluid withdrawal pipe
32 is connected to the handpiece at one end and is in fluid communication
with the fluid withdrawal passage. The other end of the fluid withdrawal
pipe is connected to a constant flow pump 34 preferably a constant displace-
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ment, variable speed, peristaltic pump The peristaltic feature acts to
avoid any contact of the operating parts with the withdrawn fluid suspension. -
Intermediate the pump 34 and the handpiece, a relief valve 36 is connected
by a T joint 38 to the fluid withdrawal pipe and is set to open to atmosphere
should the pressure differential in the fluid withdrawal pipe exceed a pred-
etermined pressure, which pressure may be from 30 mm ~g to 50 mm Hg Pref-
erably the pressure differential at which the relief valve opens is a pres-
sure of about 40 mm Hg. Constant flow capacity of the pump is preferably a
flow of from about 20 ml per min to 30 ml per minute. Flow resistivity of
the fluid withdrawal means at these preferred conditions is from about 1.33
mm Hg to about 3.0 mm Hg. Flow resistivity in the fluid inflow system is
on the order of from about 0.5 to about 2.5 mm Hg per ml per min.
We have therefore described an effective, economical system for
irrigating and aspirating the anterior chamber of the eye during an operation
involving the insortion of a handpiece through a small incision in the eye
and during which parts of the eye such as a cataract are reduced by the action
of an ultrasonically vibrating tip. With reference to further understanding
its operation, reference is now made to Figure 2 of the drawing which shows
the electrical analogue circui* which led to the fluidic control system of
this invention. It must be further understood that each part of the inven-
,~
tion functions in relation to a moderately uncontrollable set of conditions
imposed by the needs of the operative site, i.e., anterior chamber of humaD
eye and the size of the operative incision. The conditions in the anterior
chamber of the eye are analogized by two electrical elements which are a
resistive element 44 to account for flow reslstivity through the incision, ;~
and a capacitor 45 to correspond to elasticity of the eye chamber, both ele-
ments being in parallel and connected to ground at one end and at the other
end to the inflow irrigation system and the fluid withdrawal system. The
fluid inflow system is analogized by a constant voltage source 46 correspond-
ing to the fluid supply bottle set at a specified height to provide a con-
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~068572
stant pressure head; administration set resistance 47 corresponding to the
flow resistivity thereof; an inflow resistance 48 corresponding to flow res-
istivity of the inflow hosing, and a resistance 50 corresponding to the flow
resistivity of the fluid inflow manifold of the handpiece. For the fluid
withdrawal system a pipe resistance 52 corresponds to the resistivity imposed
in the fluid withdrawal piping, and the handpiece by outflow manifold res-
istance 54.
The relief valve is analogized by a diode 56 and a zener diode 58
back to back in series at one end to the fluid withdrawal pipe and at the
other end to ground (or atmosphere) The constant flow pump is analogized
by inserting a hypothetical electrical current element 60 acting as a constant
current source. In terms of the electrical analogues of the fluidic para-
meters-resistance (R~ is equivalent to flow resistance in pressure terms;
voltage (V) is equivalent to a pressure source in mm Hg; and current amperes
(I) is equivalent to flow in ml per min. Utilizing the above analogy, the
present invention has been conceived and built and various known conditions
have been related in determining the operative parameters which are described
; hereinbefore.
The system is able to accomplish the irrigation-aspiration of the
anterior chamber of the eye, while at the same time reducing transients in-
troduced by occlusions of the fluid withdrawal or aspirating system. It can
be seen that by the invention, a simplified though quite effective fluidic
control system has been provided for use in conjunction with the operative
; system described herein and in the a~oresaid United States Patent No. 3,589,
3~3 and which provides the safeguards, effectiveness, ease of use, and oper-
ative usefulness desired by the system shown in United States Paten~ No.
3,696,613.
The invention may be employed with certain modifications and var-
iations. For instance, the irrigation portion of the system may be employed
without the aspiration system. In this mode of employment flow of fluid into
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the eye is as previously described while flow of fluid out of the anterior
chamber of the eye is through the opening or incision made therein for the
insertion of the handpiece tip. A modification of the irrigation system is
shown in the drawings where a pressure means for relief of undue pressure
head is employed. The pressure means comprises a pressure relief valve 39
connected to the inflow hose 22 by a tube 40. The pressure relief valve 39
is selected to prevent undue pressure from being applied through the irrig-
ation system to the eye chamber. The analogous components shown in Figure
2 of the drawings to such a pressure relief means incorporated in the irrig-
- 10 ation system comprise a diode 62 connected to the circuit between resistors
48 and 50 and a zener diode 64 connected back to back with the diode 62. The
zener diode anod0 is connected to ground ~atmosphere). By this variation we
are able to further limit the pressure which can be communicated to the eye
chamber through the irrigation system.
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