2. • INTRODUCTION
• Phacoemulsification is an advanced technique to
remove a cataract with minimum disturbance to eye
thereby improving rehabilitation of the patient.
• Phacoemulsification is based on ultrasonic energy.
• Ultrasonic energy is produced by a piezoelectric
crystal that converts electricity into mechanical
vibration.
3. MACHINE TECHNOLOGY
1. Ultrasonic Handpiece
• The handpiece contains the piezoelectric crystal
• the ultrasonic energy produced by the crystal is transmitted along
the handpiece into the phaco needle such that the primary
oscillation is axial
• The phaco needle is hollow with the distal opening functioning as
the aspiration port.
• The phaconeedle most commonly is manufactured in 15 , 30, and
45 configuration.
• A common phacoultrasonic frequency is 47kHz.
4.
5.
6. IRRIGATION AND ASPIRATION
HANDPIECE
• The IA tip being smooth and rounded with a single aspiration
port on the side of the tip, not at the end.
• In addition to the straight tip, 45˙ and 90˙ tips are available to
allow more versatility in accessing difficult areas of cortex (i.e.
12:00 position)
• Some newer tips are being developed that are made of silicone
instead of metal. The advantage of it is that it allows to
transform the tip from straight configuration to an entire range
of curved configurations by sliding the sleeve controller.
7.
8. PERISTALTIC PUMP
• It is a simple design popularized by the heart – lung machines
used in open heart surgery.
• As the pump rotates boluses of fluid are created between
rollers and propagated in a peristaltic fashion in the direction
of rotation.
• This fluid flow creates a pressure differential at the beginning
of pump head.
• At low rotational speed, subsequent low flow rate does not
produce any appreciable vaccum unless the aspiration port is
occluded.
• As the flow rate is increased , vaccum is produced in the line
even without occlusion.
9.
10. VENTURI and
DIAPHRAGM PUMP
• It produces vaccum by ventui effect
• The advantage of the venturi pump is that it is able
to create the preset vacuum level without
occlusion of the phaco needle tip
• Because venturi and diaphragm pumps have
inherently higher flow rates, they build up vacuums in
the aspirate line without occlusion of the aspiration
port. Once the tip is occluded, a vacuum builds
up rapidly.
11.
12.
13. Peristaltic Venturi
Flow based Vaccum based
Vaccum created only when phacotip is
occulded by catract material
--Vaccum created instantly via pump once
surgeon press foot pedal
--No need of oclusion of phaco tip
Flow is constant until occlusion Flow varies with vaccum level
Drains into a soft bag Rains into a rigid cassette.
14. RISE TIME
• it is a measure of how rapidly vaccum builds up once
occlusion has occurred at the aspiration port.
• As the pump flow on peristaltic machine is increased, the
rise time will be decreased
• Venturi and diaphragm pump machines have very rapid
rise time because of inherently fast flow rates.
• Safety and time efficiency are conflicting objectives with
respect to rise time.
15.
16. Compliance
• Change of the tubing shape and volume when put under negative
pressure.
• When the tip of the phaco needle is occluded, negative pressure
will build in the tubing. The higher the compliance the more change
in the tube’s volume. When negative pressure is created highly
compliant tubing collapses on itself reducing its inner volume’s
capacity.
• When occlusion breaks, the tubing returns to its original shape and
a temporary imbalance occurs causing rapid exit of fluid from the
anterior chamber. This is called Surge
•
The higher the compliance the greater the surge amplitude during
occlusion break
17. VENT
• Vent is the mechanism in every phaco machine that
allows vacuum to be equilibrated to air or fluid in
aspiration line
• When vacuum reached to the maximum preset level
• Vent valve will open and some air or fluid will enters
into the system (VENT)
• this will happen to prevent exceeding vacuum from
present level and no more vacuum will be there
beyond preset level
19. POSITION 1
• to provide a source of fluid infusion into the eye during the
surgery.
• There is no linear control of the infusion—the infusion is
either turned on or turned off.
• The height of the infusion bottle determines the relative infusion
pressure and flow rate during the surgery.
• To keep the eye inflated during surgery, we need to ensure that
the fluid inflow rate is greater than the fluid outflow rate.
20. POSITION 2
There is a linear control of vacuum , so that the top of foot
position 2 provides less vacuum than the middle or bottom range of
the same foot position 2.
To create the vacuum and the aspiration flow of fluid, the phaco
machine must have a fluid pump. The most common types of fluid
pumps are peristaltic and venturi,
21. POSITION 3
There is linear control of the ultrasound energy level so
that more the pedal is depreesd in position 3, more
ultrasound energy, such as would be needed for denser
cataract.
Note that if the pedal is in position 3, we are already
engaging the full function of both positions 1 and 2. The
irrigation is on, and the vacuum and
as aspiration level is at its highest preset level. Ultrasound
energy should only be applied once the tip of the
phaco probe is in contact with part of the cataract.
22. • Power Means change in stroke length..displyaed in %..% means how much
% of length of tip is moving forward out of total length of tip.
eg if the stroke length of a machine is 3 mili inches( avarage phaco tip has lengh
2-4 mili-inches)s and if we use 100% phaco power means the whole 3 mili inches
is moving forward out of sleeve but if power is 20% means the tip is moving
forward by 20% of its total length i.e 0.6 mili-inch for that machine.
•
23. • More power..more distance movement of tip
…more cracking power
• Longer stroke lengths are prone to generate excess
heat. The longer the stroke length, the greater the
physical impact on the nucleus, and the greater the
generation of cavitation forces.
24. RELATIONSHIP AMONG PUMP FLOW,
IRRIGATION AND ASPIRATION
• As the phaco involves relatively a closed anterior chamber, the
aspiration flow rate directly determines the irrigation flow rate;
the more rapidly fluid is removed from the a/c, the more rapidly
the irrigating fluid must flow in to maintain the a/c.
• This relationship assumes a sufficient bottle height so that
adequate pressure is available to keep up with a given pump flow
setting.
INFLOW
. Approximately 11 mm Hg pressure (above ambient atmospheric
pressure) is produced intraocularly for every 15 cm (6 inches) bottle
height above the patient’s eye
26. PHACOEMULSIFICATION POWER
VARIABLES
• The appropriate phaco power for a given surgical case is
determined by three variables:
1. The density of the nucleus
2. The amount of tip that is engaged
3. The linear velocity of the tip during emulsification
• Using less power would cause zonular stress, as the needle would
push the nucleus without smoothly sculpting it.
• Using more power would deliver more potentially damaging
intraocular energy without any beneficial effect.
27. • The imp. Point to realize is that there is no
predetermined “correct power” setting for a given
patient; Instead, proper power delivery is determined
intraoeratively and is dependent on other variables as
listed above.
• Most nuclei have variable density, with the central
portion being most dense.
• If the amount of tip engaged and the linear velocity
of sculpting remain constant, the phaco power must
be varied while sculpting through these nuclei with
variable density.
29. Phaco ON
Ultrasound energy delivered
Jack Hammer repulsion effect
Heat generated
Phaco OFF
Aspiration of nuclear fragments
Cooling effect
No ultrasound energy
30. 250ms
in both of 2pps and 4 pps 50% of time phaco is ON and 50% of
time phaco OFF .what ever the pulse we keep total phaco ON
time will be 500ms and OFF time will be 500ms…….so by
changing pps the APT will remain constant .
That’s why if you want to reduce or increase phaco time you have
to change the duty cycle not the pps
250ms 250
125 125 125125
34. When do we want higher or lower duty cycles?
The answer depends on the phase of surgery.
For sculpting such as with the technique of divide-
andconquer, we need to deliver sufficient energy to be able to
cut the grooves. This requires a duty cycle of about 40-60%.
Once we have the grooves placed in the nucleus and we have
cracked it into quadrants, we can use a lower duty cycle during
the phaco-assisted aspiration of the quadrants.
For this quadrant removal, a lower duty cycle of 20-40% can
be used since the principal force for nucleus removal is the
fluidics and not the ultrasound.
35. The concept to remember is that a higher duty cycle results in
better cutting
power but increased heat generation and more energy-
related damage to the corneal endothelium.
Using the lower duty cycle allows more fluidic aspiration of
nuclear fragments while minimizing heat and phaco
power, resulting in clear corneas immediately after surgery.
And we all know that clear corneas on post-op day one make for
good visual acuity and very satisfied patients.
36. Decreasing US energy uses
Important for corneal endothelial protection
1)Mechanically by using CHOP technique for nucleotomy.
2) Reducing AVG phaco power by
a) limiting the foot pedal depression in position three
b) by decreasing the maximum phaco power level on the machine.
3) Reducing phaco time by
a) applying the ultrasonic power when cataract pieces are at the
phaco tip and are not aspirated by the vacuum forces alone
b) delivering smaller pulses or bursts of phaco energy instead of
continuous ultrasound.
With optimized ultrasonic phaco power parameters, it is possible to remove
cataracts with less than 1 second of absolute phaco time, yielding immediate
clear corneas and happy patients.
37. Overview of Phacoemulsification
Techniques
Sculpting angle
• The phaco needle produces occilation in an axial fashion.
• If the long axis of the needle is placed parallel to the sculpting surface, the
needle would simply vibrate back and forth over the surface without sculpting
• Minimum Groove width
The groove must be adequatly widened to accommodate the phaco needle’s
silicone sleeve. Otherwise it may get obstructed in a narrow groove that may lead
to use of unnecessary high phaco power or Pushing the handpiece harder and
stressing zonules.
38. Posterior Groove
• Like minimum groove width, the posterior groove should be adequately
deepened to accommodate the posterior contour of the phaco probe and its
silicone sleeve.
Judging Groove Depth
• Sculpting inadequately only gives false sense of security and in fact makes all
subsequent steps more difficult; both nuclear cracking and rim removal are
most efficiently accomplished after deep sculpting.
• The red reflex typically gets brighter where sculpting has reduced the
thickness of nucleus when cataract has significant nuclear sclerosis.
39. • With post. Cortical or subcapsular opacities : Gently manipulate the nucleus from side to
side and observe the movement of the posterior opacities relative to the base of the groove.
• Phaco needle can be used to estimate the groove depth.
Peripheral Groove
• The circular Golden reflex” of the hydrodemarcation makes a functional limit for
peripheral extension.
