Phacodynamics refers to the fundamental principles of inflow, outflow, vacuum, and phaco power modulation during cataract surgery. Understanding these principles helps optimize machine settings for different surgical techniques. The foot pedal controls irrigation, aspiration, and ultrasound energy. Position 1 provides irrigation only, position 2 adds aspiration, and position 3 engages ultrasound. Peristaltic and venturi pumps differ in how they create vacuum. Peristaltic pumps require tip occlusion while venturi pumps create vacuum instantly. Factors like compliance, surge, and vent type impact fluidics and safety. Mastering phacodynamics leads to independent surgical skill.

1. PHACODYNAMICS
Made Easy
Gyanendra Lamichhane, MD
Phaco surgeon and Retina fellow
Lumbini Eye Institute 1
Bhairahawa,Nepal

2. Definition
Study of the fundamental principles of inflow rates, outflow rates, vacuum,
phaco power modulation along with microsurgical maneuvers with
different types and grade of cataract.
true understanding of this will help in logical setting of the machine parameters
in adaptation to different surgical techniques
Even the most modern machine will not give adequate results as compared
to an older machine if the principles of phacodynamics are not well
understood
KHOW THE PHACODYNAMICS …….LETS BECOME INDEPENDENT ………
2

3. Foot pedal
Position 1----Irrigation( no aspiration ,no US)
Position 2---irrigation+aspiration( no US)
Position 3---irrigation +aspiration+ US
3

4. 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.
4

5. Position 2
• There is a linear control of vacuum and flow, so that the top of foot
position 2 provides less vacuum or flow 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,
5

6. There are two primary sources of fluid outflow during phacoemulsification
• the outflow from the phaco probe created by the fluid pump (aspiration
tube)
• and the leakage of fluid from the incisions.
6

7. Foot Position 3: Ultrasound Energy
• 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
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.
• When we titrate the amount of ultrasound energy we place into the eye, we
are keeping the frequency constant but we are increasing the stroke
length and therefore, the total amount of energy.
7

8. Hand Piece
Silicon sleeve
Aspiration( outflow) Irrigation
(Inflow)
80% of irrigating fluid enteres through this side port USG POWER
20%
8

9. • When we look at the phaco probe closely, we see that there are three lines
attached:
(1) the infusion tubing carrying fluid into the eye,
(2) the outflow tubing that removes the fluid via flow that is created by the
phaco machine’s fluid pump, and
(3) the line that carries the electrical signals to control the ultrasound energy
at the tip of the phaco probe. These three lines correspond to the three
phaco foot pedal positions.
9

10. 10

11. Concept of Fluidics
• The basic concept of fluidics is that the inflow of fluid must be greater than
the outflow of fluid.
• By keeping a constant infusion pressure and limiting the outflow, we can
ensure that the eye stays inflated and stable during surgery.
• If outflow > inflow, even for just a fraction of
a second -----surge
this can cause chamber instability, collapse of the eye, and aspiration of the
posterior capsule.
The primary rule for phaco fluidics
INFLOW > OUTFLOW
Source of INFLOW
bottle of BSS
Source of OUTFLOW
Aspirated fluid via phaco probe
Leakage through incision
11

12. fluidics
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
12

13. Aspiration Flow Rate
• The amount of fluid flowing through the tubing. This is reported in cubic
centimeters per minute (cc/min). With a peristaltic pump, flow is determined
by the speed of the pump. As flow increases the current in the anterior
chamber increases how well particulate matter is attracted to the phaco tip.
13

14. PARAMETRES
Flow rate( Aspiration)
how fast the things(cataract material,fluid) is coming to phaco
tip.More flow rate---rapid movement of the material to tip
Vaccum
after occlusion of phacotip by nuclear material how strongly those
material are held at tip. More vaccum -----more strong hold.
14

15. 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 milli inches( avarage phaco tip has
lengh 2-4 mili-inches)s and if we use 100% phaco power means the whole 3
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.
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. Stroke length is determined by foot pedal
excursion in position 3 during linear control of phaco.
15

16. • APT—Absolute Phaco Time
Total amount of phaco energy used
APT= EPT X AVG
EPT----Elapsed Phaco Time
AVG----Avarage phaco power
• It makes sense that if you deliver 15 seconds of energy at 100% power, it is
about the same as 30 seconds at 50% power, or 60 seconds at 25% power.
This is because for each of these three examples, the APT (Absolute Phaco
Time) is 15 seconds
16

17. Decreasing USG energy uses
(CAP)
• 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. 17

18. Power generation
• Phaco needle movement creates mechanical power. Total power is a combination of
the frequency of the needle movement and stroke length.
Frequency
• The speed of the needle movement. It is determined by the manufacturer of the
machine. Phacoemulsification needle move at a frequency of between 35,000 to
45,000 cycles per second (Hz)
This frequency range is the most efficient for nuclear emulsification.
Lower frequencies are less efficient and higher frequencies create excess heat.
18

19. Pump
• The part of the phaco machine which moves fluid through the aspiration
tubing. The pump settings control the rate of movement of the fluid.
Flow Pump
• The primary example of the flow pump is the peristaltic pump. These
pumps allow for independent control of both aspiration rate and aspiration
level.
Vacuum Pump
• The primary example of the vacuum pump is the venturi pump. This pump
type allows direct control of only vacuum level. Flow is dependent upon the
vacuum level setting.
Vacuum
• Negative pressure measured in millimeters of Mercury (mm Hg). Vacuum
determines how well, once occluded on the phaco tip, nuclear material will
be held to the tip.(holding power)
19

20. Peristaltic Ventury pump
pump
20

21. Peristaltic pump
rollers while moving
compress the phaco outflow tubing in a peristaltic manner
physically moves fluid and creates a continuous “milking” action on the fluid
column
The phaco machine can directly control this flow level, hence the term flow
based; however, the preset vacuum level is only achieved once there is
occlusion of the outflow line, typically at the phaco needle tip with cataract
material.
21

22. Peristaltic pump
• At low speeds of rotation a vacuum is not produced unless the aspiration
port is occluded. As the speed of rotation is increased( which is done only
by increasing flow rate), vacuum is produced in the aspiration line without
occlusion.
• N.B…in peristaltic pump vaccum can be produced both with or without
occlusion of phaco tip depending upon whether the tip is occluded or not.
• .if you want to built vaccum without occlusion you have to increase flow rate
and if you want to built vaccum at low flow rate you have to occlude the
tip…
SO CALLED AD FLOW BASED PUMP
22

23. As the occlusion of phacotip by catract material happens
the vacuum builds
the rollers slow down,
and the outflow level decreases
On complete occlusion
the rollers come to a stop
the outflow approaches zero, and the vacuum is at its highest level
23

24. venturi
• The vacuum level is created within a rigid drainage cassette, to which the
phaco aspiration tubing is connected . Since there is no milking of the
aspiration line, the phaco tubing can be made rigid with low compliance
• The advantage of the venturi pump is that it is able to create the preset
vacuum level without occlusion of the phaco needle tip
• . When the surgeon depresses the foot pedal, the preset vacuum level is
immediately created, hence the term vacuum based
• 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 uprapidly.
24

25. • In the venturi pump Bernoulli’s principle is applied.
• When the speed of flow of a fluid is increased in a region, the pressure there
is decreased.
• Compressed gas, such as air or nitrogen, flowing through pipe A reduces
the pressure in the region just above the tube B and creates a partial
vacuum in space C.
• There is no moving part in this pump. A B
C
25

26. Differences
• To create the preset maximum vacuum level with a peristaltic pump,
there must be complete occlusion of the phaco needle with cataract
material. To create the preset vacuum level with a venturi pump, the
surgeon simply needs to depress the foot pedal.
• Currently in the United States, the most commonly used fluid pumps are of
the peristaltic design.
26

27. Peristaltic Venturi
Flow based Vaccum based
Vaccum created only when phacotip is --Vaccum created instantly via pump
occulded by catract material 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.
27

28. • Peristaltic is DELUX CAR---SAFE AND RELIABLE
• Venturi is racing car----faster and dangerous
28

29. Diaphragm pump
• In the diaphragm pump a flexible metal or rubber diaphragm moves up and
down.
• This movement, along with the vertical motion of two valves,maintains the
vacuum
• Clinically, diaphragm and venturi pumps are very similar
29

30. • A peristaltic pump with a slower flow rate is useful for a beginner because it
provides the largest safety margin in the event of a sudden capsule
occlusion in the aspiration port.
• The slow rise time allows enough time for the surgeon to come back to
position 1 of the foot pedal or even relax.
• The disadvantage of a peristaltic pump is that it results in a longer
procedure. A peristaltic pump at a moderately high flow rate presents a
good compromise between safety and efficiency.
30

31. Rise time
• The amount of time required to reach a given vacuum preset, assuming
complete tip occlusion
• The diaphragm and venturi pumps have rapid flow rates and rise times.
• The peristaltic pump has a slower rise time, which can be made more rapid
by increasing the rotation of the wheel (i.e. at a higher flow rate).
31

32. 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 of exists 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 32

33. SURGE
• . phaco needle is occluded by nucleus matter and tubing collapses due to
negative pressure.
• When occlusion breaks after eating that nuclear piece
• The negative pressure suddenly becomes off
• the rate of fluid sucked into the phacotube from the anterior chamber can
be temporarily increased due to the sudden expansion of the tubing.
• This can cause temporary shallowing until the fluid is replaced by the
infusion ( SURGE)
Surge is the situation when the outflow
of fluid from the eye exceeds
the inflow, even for just a fraction of a
second. 33

34. 34

35. HOW TO REDUCE SURGE?
1) lower levels of flow and vacuum
2) Rigid noncompliant aspiration tubing.
3) venting.
Venting allows vacuum levels to be equilibrated to air or fluid into the
aspiration line.
A system for venting exsits in all phaco machines.
35

36. Minimizing surge
4) Increasing bottle height
5) Reducing tip size
6) ABS ( Aspiration Bypass Port) Port---small hole in metal part of phaco hand
piece so that even under occlusion some fluid will pass out through it. ABS
will function only in occluded state of tip.also has cooling effect
36

37. Vent
Like Ventilation
Occlusion of phacotip by nuclear fragment
Vaccum created
When vaccum reached to the maximum preset level
Vent valve will open and some air or fluid will entres into the system (VENT)
this will happen to prevent exceeding vaccum from present level and no more vaccum
will be there beyond preset level (ADVANTAGE OF VENT)
37

38. Which vent is good????
Air or Fluid????
When Vaccum reached to preset level
Vent valve opens
Air or fluid entres the vaccum chamber ( air vent system/fluid vent system)……suppose stage 1
Bubbles of air/fluid expands .but air expands more in vaccum in comparion to water bubble
stage 2
Once vaccum breaks( after emusification of nuclrear matter at phaco tip)and fluid enters inside
Expansion reverse …new stage 1
At this point the size of air bubble is less than water bubble( i.e air contracts more than water)
SURGE MORE WITH AIR VENT
Conclusion….FLUID VENT IS BETTER
38

39. Surge is less with fluid VENT
Air expands more in Fluid
vaccum expands
less
Once occlusion breaks
Fluid
Air contracts
contracts less
more
39

40. POWER
(Frequency x stroke length)
• Each machine has fixed rate of vibration (35000-45000/sec )
FIXED
• When we change the phaco power we are changing stroke length of phaco
tip (CHANGEABLE)
eg..
Rate of vibration(fixed for
particular machine)
10% phaco power
70% phaco power
40

41. Phaco mode
Continuous Mode
Pulse Mode
Brust Mode ----single VS multiple
41

42. Continuous mode
• All the time ultrasound is ON at gradual manner (LINEAR) depending
upopn foot pedal position 3 …….no OFF
• In Every second……. all second is full with ultrasound
Disadvantage……More USG power delivery as there is no gap
uses—for scuplting
42

43. Pulse mode
• Phaco is not on throughout all part of 1 second
• With in 1 second …in part of second phaco is ON and in another part of
second phaco is OFF….there is pause in ultrasound
• Less energy---ADVANTAGES
• Adjustable like 2 pulses/sec
4 pulses/sec
10 pulses/sec
43

44. What does it mean????
• Eg..1
If we have 2 pulses/sec…
Means in 1 sec 2 on cycle and 2 off cycle ( i.e total 4 cycle)
So each pulse is of 250 millisec..( 1sec= 1000 millisec)
Eg 2 if we have 4 pulse/sec
4 pulses/sec = 4 oncycle and 4 offcycle/sec =total 8 cycle= 1000/8m =each
pulse is of 125 millisec
End Result— in all …50% of second USG is ON and 50% of sec USG
OFF…doesn’t matter what pulse u have set..
44

45. • Pulse of energy are delivered at definite rate of pulses per
second(pps),which is the number of cycles per second
• The defult cycle for pulse mode is to have phaco energy on and off
for equal period(50:50),thus giving a duty cycle of 50%
45

46. Phaco can be delivered in
• Panal mode
• Surgeon mode
46

47. PANAL MODE……When you introduce your foot pedal to stage 3 the whole energy will
be delivered to maximum (i.e from beging of stage 3 to end of stage 3 constant
power)
SURGEON MODE or LINEAR MODE..…when you push foot pedal to stage 3..the phaco
enery will be deliver gradually
Eg.. When you set phaco power of 60%
in Panal mode …when you go to stage 3 in foot pedal whole 60% will be delivered at a
time but in ( it doesn’t matter whether you are in beginning or end of stage 3)
surgeon mode the power will built up gradually like 10%...20%....30
%....40%.....50%....60%... As you gradullay push the pedal…ie 10% as you enter in
beginning of stage 3 and increasing finally reaching to your preset level of 60% when
your foot pedal is at end of stage 3
47

48. Panal mode
60% 60%
Foot pedal in position 3 early stage Late stage of foot pedal 3
48

49. SURGEON or LINEAR MODE
Between 2 pulse interval is equal
60%
10%
49

50. Linear mode pulse
50

51. Hyperpulse
• Hyperpulse allows the surgeon to choose from new, higher-range pulse
settings that can exceed 100 pulses per second (compared with traditional
pulse, which had a maximum of 20 pulses per second).
• The surgeon does not change the amount of phaco energy used by using
more pulses per second because each short phaco pulse is followed by a
short phaco-off time.
• The increased frequency of phaco-off periods does, however, reduce the
amount of heat generated
51

52. BRUST MODE
Ultrasound……long period of no ultrasound….ultrasound
BRUST WIDTH
30----500 milli Sec
USG USG
52

53. If you are in early stage of foot pedal 3…there will be off period( interval
between pulses) of 2.5 milisec.
As the foot pedal goes down the off period will be shortens
At the end there will be no off periode…brust mode will become continuous
mode.
53

54. For brust mode
If foot pedal is in late stage of position 3
As phaco will convert to continuous mode…no off…used for sculpt
If foot pedal is in mid stage of position 3
now some interval between phaco pulse develop …quardrant removal
If foot pedal is in early stage of position 3( pedal just pressed in 3)
Long gap between……epinucleus removal,chop,bringing material in
centre
54

55. 55

56. Single Vs Multiple brusts
• Single burst delivers just one single burst of energy, for burying the phaco
probe into a nucleus for chopping. (not preferrable)….doesn’t matter
whether you are in early or late stage of foot pedal position 3….one and only
1 brust …then finished
• multiple burst mode delivers one single burst by just entering foot position
3, and still have the ability to deliver many more bursts at varying
intervals with further foot pedal depression
56

57. • Because the phaco foot pedal now controls the rest interval between
identical bursts, we do not have linear control of the phaco power level.
• For this reason, it is important to use a lower phaco power setting when
using burst mode as compared to pulse or continuous modes.
• When the foot pedal is maximally depressed, the rest interval between
bursts is zero and the phaco probe essentially delivers continuous energy
57

58. • For my technique of quick chop, I typically use just one phaco setting:
multiple burst mode with a burst time of 20 milliseconds, a power of 10%
and an endpoint duty cycle of 50%
• . This means that I can give 50 of these identical bursts in 1 sec at 10%
power which is equivalent to doing phaco in continuous mode of 1 sec
at 10% power
• This low energy delivery in burst mode makes surgery safer by minimizing
heat production and by minimizing endothelial cell damage from the
ultrasound power.
• This translates to clear corneas immediately after surgery, better visual
outcomes, and most important, higher patient satisfaction. I encourage you
to try burst mode.
58

59. Hyperpulse and Hyperbrust
• The concept of pulse and brust has been more modified in new machine.
• Old machine had maximum pulse of 20 pps but new has upto 120 pps.
• Old machine had brust width as narrow as 30milisec whereas new has 4
ms.
• advantage of this upgraded range of programmability is the smoothness and
precision of power delivery
59

60. Hyperburst
• Hyperburst technology allows you to use burst durations as short as 4 ms
(compared with traditional burst, which had a minimum of 80 ms max 600).
• These "microbursts" are very small amounts of phaco energy that reduce
the total amount of energy used, and the "microrests" allow for dissipation of
thermal energy .
60

61. • . If we want to harness the sculpting and cutting ability of the phaco hand-
piece for grooving of the cataract nucleus, it makes sense that a knife with a
smooth blade would cut well.
• A coarsely serrated knife with large, widely spaced serrations would not cut
as smoothly.
• However if we use a very finely serrated knife, it would likely cut the best of
all. Using a very high pulse rate of 100 or more pulses per second results in
the cutting ability of a very finely serrated knife, yet delivers half of the
energy of continuous phaco power.
ADVANTAGE…we get continous phaco effect delivering half energy
NB..by changing PPS we cant can’t change the APT.
61

62. NB..in continuos and in pulse phaco energy is
increasing linearly but no linear in brust…that’s brust
62

63. 63

64. • Phaco ON
Ultrasound energy delivered
Jack Hammer repulsion effect
Heat generated
Phaco OFF
Aspiration of nuclear fragments
Cooling effect
No ultrasound energy
64

65. Repulsive Vs Attractive forces
When power on….Repulsive force acts ( emulsification + heat generation)
When power off… Phaco ON—repulsion
Phaco OFF--attraction
attractive force acts
brings the nuclear matter to phaco tip
Vaccum builds up
Mechanical removal of material,no heat and surge occur during attractive force
65

66. Vaccum and bottle height
VACCUM BOTTLE HEIGHT
(mm/Hg) (In Centimeters)
150 65
200-250 85
250-300 110
66

67. Use of pulse
Long OFF(or short ON) eg…2 pulse/sec
attractive force come on play for long time…used for chopping or to bring
material to central area before removing
Short off (or long ON) eg…6 pulses/sec
for sculpt and quadrant removal
So long OFF for better hold and short OFF just to clear materials.
67

68. Changing the PPS doesnot change the absolute phaco
time
250ms 250
250ms
250 ms
2PPS
125 125 125 125
4 PPS
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
68

69. Changing duty cycle can change APT
50%
50%
50% duty cycle
20
% 80
%
20% duty cycle
Both has 4 pps but duty cycle in 1 is 50% and 2 is 20% 69

70. 250ms 250 2PP
250ms ms 250ms
Ratio ON to OFF is 50:50,hence 50% duty cycle
100 100
ms ms
2PP
400ms 400ms
Ratio ON to OFF is 20:80,hence 20% duty cycle
In 1 sec total on 200ms and total off 800 ms .
70

71. The amount of phaco energy affects corneal endothelial cells so the
goal is to use just enough ultrasound
71

72. How ??????
1) Use mechanical division
D& Q,Chop
2) Use high vaccum
3) The phaco tip used
4) Use pulse or brust mode not continuous
5) Modify US delivery
72

73. Phaco tip
Standard tip (19 guage)
Outer diameter(OD)----1.1 mm
Inner Diameter( ID)-----0.9 mm
Micro tip( 21 guage)
OD---0.8mm
ID----0.6mm
ADVANTAGE of Microtip
Smaller incision
DISADVANTAGE
Less holding force for same power setting
Less amount of material/time
73

74. Modifying US Delivery
• By changing duty cycle
ON ON
PULSE DURATION
OFF
PULSE DURATION
INTERVAL ( Between 2 on part)
CYCLE TIME 74

75. • Frequency—number of pulse/sec
• Duty Cycle---time during which power is on as % of cycle (traditionally 50%)
i.e 50% time USG ON…50% OFF
• Pulse duration- time of phaco power on (PYRAMID)
• Interval duration —time from one pulse to another
• Cycle time —pulse duration+interval duration
N.B--- in cycle time pluse duration is added to interval where as in interval
we exclude pulse duration
75

76. Change in duty cycle
• Duty cycle 50%....means 50% time USG on…50% time no USG
• Duty cycle 20%---20% time Phaco ON…80% time OFF
• 2 Pulse /sec---means 1 sec is divided in 2 part
• 4 Pulse/sec---means 1 sec is divided in 4 parts
76

77. Duty cycle
phaco-on time
phaco-on time + phaco-off time
77

78. Changing duty cycle
50% duty cycle
50:50
20 20% duty cycle
on 80% off
20:80
Both duty cycle have 3 pulses/sec in upper
fig.50% time phaco on whereas in lower 20% 78
time

79. 79

80. 250ms 250 2PP
250ms ms 250ms
Ratio ON to OFF is 50:50,hence 50% duty cycle
100 100
ms ms
2PP
400ms 400ms
Ratio ON to OFF is 20:80,hence 20% duty cycle
In 1 sec total on 200ms and total off 800 ms .
80

81. • For example, if I am using 10 pulses per second and I’d like to slightly
reduce the ultrasound energy,
• I can decrease it from a 50% duty cycle to a 40% duty cycle. This can be
done by dropping the duty cycle ratio as seen on the control panel of
the phaco platform
• . Alternatively, I can delineate the specific on and off periods for each cycle,
with an on-time of 40 milliseconds followed by an off-time of 60 milliseconds,
I will achieve the same result—a total cycle time of 100 milliseconds, with 10
pulses per second and a 40% duty cycle.
• NB..if i change the PPS I cant reduce APT as explained before so I have to
reduce duty cycle
81

82. 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%. (MORE DUY CYCLE)
• 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.( LOWER DUTY CYCLE)
82

83. 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.
83

84. • For grooving and sculpting of the nucleus, the work is being done by the
ultrasonic energy and thus the flow and vacuum settings are quite low –
just enough to aspirate the nuclear material removed from each forward
stroke of the phaco probe.
• A vacuum level of less than 100mmHg and a flow rate of less than
30cc/min is sufficient for this purpose
• For quadrant removal, a moderate amount of holding power is required to
bring each quadrant into the phaco tip. Using a higher vacuum level of
200-300mmHg and a flow rate of 30-50cc/min, depending on the needle
size, is typically sufficient for this purpose.
84

85. • For phaco chop, holding power of the nucleus is important in order to
securely fixate it while using the chopper to mechanically disassemble the
nucleus.
• This requires a relatively high vacuum, such as 200-250 mmHg with the
1.1mm needle, or 300-400mmHg with the 0.9mm needle.
• Once the nucleus has been broken into smaller fragments, the speed at
which the fragments are attracted to the phaco tip is determined by the
peristaltic flow rate, with 20cc/min being very slow and 50cc/min being very
fast.
• The same vacuum and flow rate settings can be used for the entire nucleus
removal procedure during phaco chop.
85

86. Variable rise time and custom setting
• To reduce the repulsive force of phaco we can decrease the phaco power,
but this isn’t always the best answer, particularly when a nucleus is dense
and requires more phaco power for emulsification.
• Instead, if we initially attack the nucleus with lower power, then hold on
to it with the vacuum fluidics of the phaco machine, we can ramp up
the power to a higher level.
• The new phaco power modulation software on most platforms allows this
automatically, with millisecond precision. Burst and pulse modes deliver
square-wave
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87. clear corneal Incision
• Easy to construct
• Good assess to cataract
• Seal well
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88. SCULPT
• high pulse mode (80 PPS or more), with a 40-60% duty cycle,
• maximum phaco power of 40-60%.
• The fluidics should allow for a low vacuum and low flow setting to simply
evacuate any emulsified cataract bits from the excavated trench.
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89. CHOP
• To chop each half, we need to change the phaco and fluidic settings:
• here a burst mode is my preference as it affords using very little energy.
A short burst width of 4-20 milliseconds and a power of 10-40% works well.
For those surgeons preferring a pulse mode,
try 10-20 PPS (pulses per second), 30-50% duty cycle, and a maximum power
of 20-50%.
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90. • The fluidics must also be changed to increase the holding power of the
nucleus.
• Try using a higher vacuum level (200-400 mmHg depending on your phaco
needle size), and a higher flow rate (30-50 cc/min) with a corresponding
higher bottle height to ensure that the inflow is greater than the outflow
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91. UltraSound Power
Fixed Machine setting
• The variable that is controlled is set and when the foot pedal is pushed the
machine produces the preset amount of ultrasound power or aspiration flow
rate. (this can be used when referring to power and aspiration flow rate.)
Surgeon Controlled Machine setting
• The amount of ultrasound and or aspiration is controlled by the surgeon by
pushing down the foot pedal. Also referrerd to as variable control.
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92. Typical Power Modulation Settings
• The following are a few typical settings on the Alcon Infiniti Vision System:
sculpting,
a maximum preset power of 60 percent with 60 pulses per second and a
duty cycle of 50 percent
quadrant removal, a maximum preset power of 40 percent with 10 pulses per
second and a duty cycle of 35 percent
epinucleus, a maximum preset power of 20 percent with 10 pulses per second
and a duty cycle of 25 percent
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93. LETS ENJOY THE CHARM OF PHACO
THANK YOU
Meet me-- yourgyanu@gmail.com
Facebook—gyanu raja
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