Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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The present invention relates to a method
and apparatus for conducting microsurgery, and in
particular, for incising human and animal tissue with a
focused light beam.
In particular, because of sharp focusing and
high power, laser beams are at present used to incise
material. Thus, on the one hand, laser beams are used
in the manufacture of components for electronics, and
in particular, in the manufacture of integrated
circuits. In medicine, and particularly in
ophthalmology, they are used for heat coagulating the
retina and disrupting a membrane of a cataract.
If lasers, with laser beams of long pulse
duration, are used (e.g., thermal lasers), the energy
converted at the target point as heat also has an
effect in the adjacent areas whereby a desirable heat
coagulation of the incision walls is achieved, but
undesirable material changes can occur outside the
incision.
If lasers with very high power laser beams
are used (e.g., Q switched lasers), rapid incisions can
be made. However, the incision walls can be very
unstable, particularly in soft materials, since the
incision walls have not undergone any stabilization by
heat. ~:
In the case of materials containing much
fluid, human or animal tissue, fluid, such as blood, ~f ,
etc., penetration into the incision is effected when ;;
incising by means of a high power laser beam which is ~ ;
not coagulatedj thus leading to problems, in
particular, hindrances in the application of a laser. -
When the tissues of the human eye or of the
human or animal body are subjected to repeated appli-
cations of a thermal tlong pulse duration) or a i ;~
photodisruptive type (short pulse duration) of laser,
it becomes obvious that the same laser discharge on the
same tissue achieves progressively diminished results. -
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In the case of the thermal (Ar) laser, it is due to an
increased blanching of the tissue that the beam is
reflected. In the case of the photodisruptive laser
(YAG), it is the debris within the cut created by the
laser and pressure from the adjacent tissue that
prevents efficient tissue tunneling. Neither type of
laser is able to achieve by itself efficient tunneling
through solid tissue.
Surgical treatment requires the ability to
create channels through solid tissue to form shunts and
bypasses for the passage of body fluids or to penetrate
through tissue to reach the object of surgery.
It is an object of the present invention to
provide an apparatus for incising with a sharply
focused laser beam, with which in particular blood
fluid containing tissue can be cut with high
efficiency.
A method in accordance with the present
invention includes the steps of causing an incision in
animal or human tissue comprising the steps of
producing a first laser beam from a laser source
consistiny of one of a photodisruptive laser and a
thermal laser directing the first laser beam to the
target area for a predetermined pulse duration and
immediately successively producing a second laser beam
from a second source consisting of the other
photodisruptive laser and the thermal laser for a pulse
of a predetermined duration to complete a cycle for a
complete duration of one second or less, and repeating
! ' 301 the cycle.
In a more specific embodiment of the present
method, the first and second laser beams are directed
confocally onto the target area in alternating pulses.
An apparatus in accordance with the present
invention comprises a housing, a first laser means
producing a photodisruptive laser beam, a second laser
means producing a thermal laser beam, means for
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directing the laser beams from the first and second
laser means along a confocal path from the housing to a
target, switching means for alternately directing the
photodisruptive beam and the thermal beam in successive
pulse durations for a complete cycle of a duration of
one second or less.
In a more specific embodiment of the present
invention, the thermal laser is an Argon laser while
the photodisruptive laser is an Nd:YAG laser.
The alternative application of different
types of lasers is of advantage. The energy of the
laser beam of the thermal laser is converted in the
tissue to heat.
It has been found that the alternating
treatment of successive Argon laser beams and Nd:YAG
laser beams allows a deeper incision in the tissue. If
an Nd:YAG laser discharge precedes an Argon laser
application, the Nd:YAG laser cuts the tissue while the
Argon laser coagulates the tissue. The cut of the
Nd:YAG laser then penetrates the photocoagulated tissue
at the target and reaches a deeper stratum which is not
affected by the previous coagulation. The Argon laser
beam passes through the incision and is efficiently
absorbed, and the repeated alternating effect of the
Argon-Nd:YAG laser discharges creates a cavity in the
tissue with coagulated tissue walls.
The subsequent discharge of photodisruptive
energy by the Nd:YAG laser of a second alternating
cycle provides an implosive force within the same
30~ space. It disrupts the coagulated walls and expands
the tunneling further. This action creates favourable
conditions for another alternating laser cycle for
further penetration.
The combined forces of the alternating beams
is greater than each separate laser can provide alone.
The explosive pressure of the Argon laser depends on
discharge in the narrow space provided by the Nd:YAG
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laser's incision. The efficient transformation of
these forces into mechanical energy prevents laser
radiation overdosage.
It has been found that the alternating cycle
of the laser beams must be accomplished within a time
span of less than one second.
Having thus generally described the nature
of the invention, reference will now be made to the
accompanying drawings, showing by way of illustration,
a preferred embodiment thereof, and in which:
Fig. 1 is a schematic diagram of a typical
arrangement for producing two alternating laser beams
of different wave lengths; and
Fig. 2 is a schematic diagram of a typical
robotic switching device which could be used with the
apparatus illustrated schematically in Fig. 1.
Referring now to the drawings, there is
shown a housing 10 within which is provided a typical
Argon laser 12 and an Nd:YAG laser 14. A control panel
16 is arranged in the housing. The control panel
includes manual command keys for the YAG laser
(COHERENT System 9900). These command keys may include
a STANDBY key 26 and a DISCHARGE key 28. A READY key
30 and an ARGON key 32 are also provided in line on the
control panel. A robotic switching device 34, as shown
in Fig. 2, would be located over the manual keys as
shown in dotted lines in Fig. 1. The robotic device 34
would include piston and cylinder arrangements 36, 38,
40, and 42, which correspond to manual keys 26, 28, 30,
30~ and 32. The piston and cylinder arrangements, as is
well known, may be pneumatic and may be electronically
or electrically activated and may be controlled by a
computer (not shown).
In order that the beams produced
respectively from the Argon laser 12 and the YAG laser
14 be confocal, a series of mirrors 18, 20, 22, and 24,
which are well known from the prior art, are located in
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order to direct the laser beams as required. An on-off -
trigger 44 activates the sequence, but a controllinq
foot switch 46 may be provided in order to include a - :
double safety control ~ -
The robotic device 34 is included in order :
to provide a cycle within one second which includes in
one typical sequence the activation of the STANDBY key ~
26 by means of the corresponding piston 36 in the robot .
device 34 followed by the activation of the ARGON key
10 32 by the respective piston 42. This activation will ; ~:
provide the first laser discharge, and then the READY . .
key 28 must be activated by the respective piston 38 in ~.
order to discharge the YAG laser beam by means of the :: `i
YAG key 30. The cycle is repeated by starting over: .
again with the STANDBY key 26. :
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