Introduction to phacodynamics and techniques

1. PHACODYNAMICS
Haitham Al Mahrouqi
April 2018

2. REFERENCES
➤ AAO BCSC: Lens and cataract
➤ All India Ophthalmological Society: A guide to phacoemulsification. Can be
accessed from http://www.aios.org/cme/cmeseries21.pdf
➤ Phaco Fundamentals for the Beginning Phaco Surgeon. By Uday Devgan

3. UNDERSTANDING PHACOEMULSIFICATION
➤ Phacoemulsification is a dynamic procedure requiring understanding of the:
➤ Machine
➤ The functions of the machine

4. PHACODYNAMICS
➤ Definition
➤ The various functions of the phaco machine and their inter relationship
➤ Functions of phaco machine:
➤ Ultrasonic power
➤ Irrigation and aspiration system (A.K.A fluidics)

5. ULTRASONIC POWER
➤ Phaco power is generated by vibrations of quartz
crystals in the hand piece.
➤ Quartz is silicone oxide and is peizoelectic: That
means if you squeeze a quartz crystal, it generates
a tiny electric current. The opposite is also true: if
you pass electricity through quartz, it vibrates at
a precise frequency (it shakes an exact number of
times each second).
➤ As well as being used in watches to calculate each
second, it is used in the phaco tip.

6. ULTRASONIC POWER
➤ The frequency of quarz crystal vibrations is variable from
29–60 KHz in different machines.
➤ High frequency of vibrations (from more quartz crystals
or more electric power) results in better cutting but may
result in more heat generated.
➤ In each machine the vibrations (oscillations) are fixed
but the power is modulated by changing the stroke
length (axial or torsional).
➤ Power = oscillations (fixed/constant) x stroke length
➤ Energy: power x time

7. MECHANISM OF EMULSIFICATION
➤ Jack-hammer: Mechanical bombarding
of the tip (axial or torsional).
➤ Cavitation: Mainly by axial movement
of the tip.
➤ Acoustic wave of fluid: From the
forward (little with tortional)
movement of the tip pushing fluid away
which can integrate soft lens matter.
Jack Hammer effect: The
rapid to and fro movement of
the tip bombards the tissue in
front and disintegrates it
Cavitation phenomenon:
The frequency of oscillation
is 40,000/ second. The swift
backward movement of the
tip results in a cavitation
phenomenon causing an
implosion of surrounding
tissue.

8. WHAT IS OZIL IP?
➤ Pure torsional jackhammer effect clogs
the needle.
➤ OZIL IP is an intelligent system
sensing that the needle is clogged and
vacuum rises where which it will
activate the axial oscillation for
cavitation.
➤ Advantages: More efficient cutting, less
heat and more stable AC.
Jack Hammer effect: The
rapid to and fro movement of
the tip bombards the tissue in
front and disintegrates it
Cavitation phenomenon:
The frequency of oscillation
is 40,000/ second. The swift
backward movement of the
tip results in a cavitation
phenomenon causing an
implosion of surrounding
tissue.

9. PHACO TIP
➤ The higher the angulation the lesser the
holding power and the more the cutting and
visa versa.
➤ For divide and conquere: use 45* (trenching is
important)
➤ For stop and chop: use 30* (holding is very
important).

10. POWER DELIVERY
➤ Power = oscillations (fixed) x stroke length
➤ Two modes for power delivery:
1. Surgeons mode (A.K.A linear /continuous):
the power varies from 0 - maximum
according to the depression in the foot pedal
in position.
2. In the panel mode: power is maximum in all
of position 3.
Extent of depression of position 3
Phaco power
Phaco power
Extent of depression of position 3

11. POWER DELIVERY
➤ Variations of the continuous mode include
pulse mode: variable intervals of on and off
at a particular phaco power (equal on and
off time).
➤ Variation of the panel mode include the
burst mode, however, now can be also made
into a linear mode: Depression on the foot
pedal in position 3 varies the time between
the intervals.
➤ Both are aimed at decreasing the absolute
phaco time (energy) as well as using the
vacuum to help with removal of the cataract.

12. POWER CALCULATION
➤ Calculate the absolute phaco time
(energey) if in 1s there are 5 pulses of
100ms duration and a similar pauses of
phaco.
➤ 5 x 100ms = 0.5s
➤ In phaco machine:
delivered
long the
it is de-
ntial pulse
de is that
s a period
tween in-
Alternat-
s heat and
s the same
creases as
oot pedal
ween each
using bu
modes.
the rest
probe es
For surg
surgery,
during g
energy
remove
depresse
power a
epi-nucl
tered, an
removal
Most ph
single b
just one
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can still
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many m
foot-ped
Figure 1
Figure 1 Figure 2
Figure 3 Figure 4

13. FLUIDICS
➤ Fluidics in phaco refers to the integrated system of irrigation and aspiration
where the A/C volume is kept stable.
➤ Phaco has a major advantage over ECCE in that it is performed in a closed system
thus avoiding damage to the cornea, iris…etc.

14. IRRIGATION
➤ The inflow of BSS into the eye is governed by the
pressure gradient at the tip of the phaco probe:
that is the pressure difference between the
positive pressure created by the bottle height
(gravity) and the negative pressure created by the
aspiration port.
➤ Newer machine have an active infusion where
there is a sensor at the phaco tip. This allows
active control of the IOP during the surgery.

15. IOP CALCULATION
➤ What is the IOP in the A/C when the bottle height is 60cm?
➤ 60 cm = 600 mm water column, 600/13.6 = 44 mmHg (Roughly 75% of the
bottle height).

16. WHAT IS THE PROBLEM WITH EXCESSIVE BOTTLE HEIGHT?
➤ Increased irrigation leads to:
➤ Pushing the iris lens diaphram leading to zonular stress
➤ Irritation to the iris resulting in miosis
➤ Overfilling the A/C leads to excessive leaking and iris prolapse.

17. WHAT IS THE PROBLEM WITH TOO LOW BOTTLE HEIGHT?
➤ reduced irrigation leads to:
➤ Fluctuations of the IOP with A/C collapse
➤ Injury to the introcular structures

18. ASPIRATION SYSTEM
➤ To emulsify the cataract:
1. There needs to be lavage (sucking) of the cataract to the tip
of the phaco probe: This is governed by the flow rate.
2. Holding power of the cataract to the phaco tip so it does not
slip away: This is governed by the vaccum created by the
phaco machine.
➤ Therefore there are two types of aspiration systems
(pumps):
1. Flow based system: Peristaltic
2. Vacuum based system: Venturi
T
he primary microscope controls are focus,
zoom, and centration. Additional functions in-
clude the ability to turn the microscope light
on/off as well as to adjust the brightness. The micro-
scope should be reset and centered at the beginning of
the case in order to provide a full range of adjustability.
Avoid high magnification for routine cases as this will
unnecessarily limit your field of view.
The more important pedal during phacoemulsification
is the phaco foot-pedal as it controls the irrigation, as-
piration, as well as ultrasonic power delivery. Fine con-
trol of fluidics and power can be achieved with prac-
tice. The three positions of the phaco foot-pedal are:
1-irrigation, 2-aspiration, and 3-ultrasound. Each step
is additive, so when we are in position 2, we have irri-
gation plus aspiration, and in position 3, we have irriga-
tion, aspiration, and ultrasound power delivery.
The irrigation in position 1 is either on or off—there
is no ability to titrate the amount of irrigation via the
foot-pedal. You will recall that the irrigation inflow is
determined by the bottle height and the size of the inflow
tubing. Taking the foot off the pedal completely is called
position zero since the phaco probe is doing nothing.
Phaco Foot Pedal Function
Irrigation = 1
Aspiration = 2
Ultrasound = 3
U
Ultras
Irrigat
O
Aspira
Aspira
A
U
Figure 1

19. VACUUM BASED PUMP : VENTURI
➤ Direct control of the vacuum and indirect
control of the flow rate.
➤ The amount and speed of gas through the
tubing governed by the depression in position
controls the amount of vacuum and thus flow
rate.
➤ The relationship of the vacuum created to the
flow rate is not linear (modified by the port
size and tubing).
➤ The advantage of this system is that the
vacuum is directly transmitted to the tip from
the system ensuring a better followability.

20. FLOW BASED PUMP : PERISTALTIC
➤ Direct control of the flow rate and indirect
control of the vacuum (only max can be set).
➤ Flow rate is the amount of fluid aspirated from
the A/C per unit time.
➤ The rollers compress the silicone tubing to
withdraw the fluid in the drainage bag. The
larger the depression in position 2 the faster the
movement of the rollers and thus higher flow
rate.
➤ Vacuum is only built up when the tip is occluded
and negative pressure builds inside the tubing.

21. FLOW RATE IN PERSTALTIC PUMP
➤ Normally between 20-36 cc/min
➤ What happend if flow rate is slow?
➤ Slow surgery and flowability to the tip is decreased
➤ What happens of flow rate is too fast?
➤ Surgery will be uncontrolled and cataract pieces may slip away as the rollers may
slip from the tubing decreasing the effectiveness.

22. VACUUM
➤ Double edge sword
➤ How does vacuum in peristaltic pump build?
➤ Only after occlusion. It governs the holding power.
The rise time to the maximum vacuum is governed
by the flow rate.
➤ How does the phaco port size affect the vacuum?
➤ Inversely proportional

23. FLOWABILITY
➤ A concept to refer to the tendency of the
cataract fragments to be attracted to the phaco
tip.
➤ The positive pressure due to the infusion and
the negative pressure created by the aspiration
pump are responsible for the creation of a
pressure gradient at the tip.
➤ This in turn leads to eddy currents from the
infusion orifice to the phaco tip.
➤ The area encompassed by these eddy currents
is known as the zone of followability
➤ Any other areas of no followability?

24. TUBINGS
➤ To maintain a formed A/C:
Inflow of BSS (irrigation) > outflow (aspiration) + wound leak

25. TUBINGS
➤ Poiseuille’s law: Resistance to flow

26. TUBINGS
➤ Describe the difference in phaco tubings and
why?
I
n order to maintain this flow balance, where the
inflow is always greater than the outflow, we can
use different sized tubing. If we look at the inflow
tubing we notice that it is significantly different than
the outflow tubing.
INFLOW
The inflow
and the tub
ing is to pr
situations.
inflow tub
sion bottle
The outflo
the tubing
Because th
of the tubi
ensure tha
flow tubin
a low com
maximum
is determin
and can ea
This high
flow tubin
pliance. W
rebounds b
el drops, t
dangerous
Figure 1

27. SURGE
➤ Post occlusion surge occurs during occlusion
of the phaco tip with a nuclear fragment and
vacuum builds up; the pressure inside the
outflow tubings is high with collapse of its
walls. Once the fragment is removed, the
tube rebounds creating -ve pressure and A/C
collapses risking injury to posterior capsule.
of tubin
monly
once th
surge o
is one o
during
PHACO
The siz
fluidics
tant thi
that the
to the f
the size
change
co need
tors equ
the larg
0.9mm
Figures 2, 3, 4

28. HOW TO PREVENT SURGE?
1. Tubings
2. Using of cassette (to decrease the
compliance of the tubings)
3. Smart machine:
A. Venting
B. Delay the start of the motor following
occlusion break
C. Different settings of the flow rate/
vacuum before and after occlusion
breaks

29. HOW TO PREVENT SURGE?
4. Smart Surgeon
• Awareness of the phacodynamics
• Decreasing the effective flow rate by using lower phaco tip.
• Using viscoelastic to decrease the inflow of BSS and surge
• Proper wound construction
• Foot pedal control

30. DIAPHRAGM PUMP
➤ Consists of a flexible diaphragm overlying a fluid chamber with 1-way valves at
the inlet and outlet.
➤ The diaphragm moves out, creating a relative vacuum in the chamber that shuts
the exit valve, causing the fluid to flow into the chamber.
➤ The diaphragm then moves in, which increases the pressure in the chamber and
closes the intake valve while opening the exit valve
➤
CHAPTER 7: Surgery for Cataract • 109
The diaphragm pump consists ofa flexible diaphragm overlying a fluid chamber with
1-way valves at the inlet and outlet. The diaphragm moves out, creating a relative vacuum
in the chamber that shuts the exit valve, causing the fluid to flow into the chamber. The
diaphragm then moves in, which increases the pressure in the chamber and closes the
intake valve while opening the exit valve (Fig 7-17). This type of pump system produces
a slower rise in vacuum. With continued occlusion of the aspiration port, however, the
vacuum will continue to increase in an exponential manner.
The Venturi pump (Fig 7-18) creates a vacuum based on the Venturi principle: a flow
of gas or fluid across a port creates a vacuum proportional to the rate of flow of the gas.
This system produces a rapid, linear rise in vacuum and allows for instantaneous venting
to the atmosphere that immediately stops the flow through the port. The vacuum is not
flow-based and builds according to the machine setting.
In general, all of these pumps are effective. The vacuum rise time (the amount of
time required to reach a given level ofvacuum) varies among the different pump designs
(Fig 7-19). In planning a specific technique, the surgeon should consider the relationship
between the aspiration flow rate and the rise time of the instrument. The vacuum rise
time is inversely proportional to the aspiration flow rate. As the aspiration flow rate is
decreased by half, from 40 to 20 mL!minute, the vacuum rise time is doubled, from 1 to
2 seconds (Fig 7-20).
Figure 7-17 The diaphragm pump. !Redrawn with permission from Practical Phacoemulsification: Proceedings
of the Third Annual Workshop. Montreal, Quebec: Medicopea International; 1991.43-48)
To cassette

31. TECHNIQUES OF NUCLEUS REMOVAL DURING PHACO
➤ Divide and conquer
cisional area
ongest length
of the capsu-
nue to sculpt
The average
lly and shal-
oves that are
order to fa-
co probe and
us 90 degrees
he first. Once
will form a +
ur quadrants.
econd instru-
th the phaco
too shallow,
eces will not
e the instru-
ll apart. This
aration of the
Divide-and-Conquer for nucleus removal.
NARROW
GROOVE
WIDER
GROOVE
Rotate & Create 4 Quadrants
Maintain the Squared Grooves to facilitate
cracking of the nucleus into quadrants.
2 HALVES 4 QUADRANTS
Starting the Grooves
Start the groove as close to the incision as
possible for a longer groove length
TYPICAL BETTER
Widen the Grooves
Allows more room for placement of the
phaco probe and second instrument.
Place Instruments
Deep in the Groove
Deep placement allows for comlete
cracking and separation of the nuclear pieces
SHALLOW DEEP
BAD
incomplete crack
GOOD
complete crack
Figure 4
tart the groove as close to the sub-incisional area
s possible so that the groove has the longest length
ossible. Be careful not to hit the edge of the capsu-
orhexis with the phaco probe, and continue to sculpt
he grooves deeper into the lens material. The average
ens is approximaately 4mm deep centrally and shal-
ows peripherally. You should create grooves that are
t least half the depth of the nucleus in order to fa-
ilitate cracking. [ Figures 1, 2 ] Use the phaco probe and
he second instrument to rotate the nucleus 90 degrees
nd make a second groove orthogonal to the first. Once
ompleted, the two intersecting grooves will form a +
gn and will segment the nucleus into four quadrants.
o crack the nucleus into quadrants, a second instru-
ment is placed into the groove along with the phaco
robe tip. If the instruments are placed too shallow,
he crack will be incomplete and the pieces will not
eparate. The proper method is to place the instru-
ments deep within the grooves then pull apart. This
will result in a complete crack with separation of the
ucleus into distinct pieces. [ Figures 3, 4 ]
Use the phaco probe’s vacuum to bring the pieces out
of the capsular bag and to the iris plane. This is the
ideal location to phaco-aspirate the nuclear fragments,
as it is far from both the corneal endothelium and the
capsular bag. Continue to bring the quadrants to the iris
plane and phaco-aspirate them. This is the technique of
Divide-and-Conquer for nucleus removal.
Widen the Grooves
Allows more room for placement of the
phaco probe and second instrument.
NARROW
GROOVE
WIDER
GROOVE
Rotate & Create 4 Quadrants
Maintain the Squared Grooves to facilitate
cracking of the nucleus into quadrants.
2 HALVES 4 QUADRANTS
BAD
incomplete crack
GOOD
complete crack
Starting the Grooves
Start the groove as close to the incision as
possible for a longer groove length
TYPICAL BETTER
Widen the Grooves
Allows more room for placement of the
phaco probe and second instrument.
Place Instruments
Deep in the Groove
Deep placement allows for comlete
cracking and separation of the nuclear pieces
SHALLOW DEEP
BAD
incomplete crack
GOOD
complete crack
Figure 4

32. TECHNIQUES OF NUCLEUS REMOVAL DURING PHACO
➤ Stop and chop
T
he technique of Stop-and-Chop uses a groov-
ing technique to make a single linear trench in
the cataract nucleus. The surgeon then stops,
divides it into two halves, and then chops each half fur-
ther. This is an easier transition for most surgeons and
results in more efficient surgery. Once the technique of
Stop-and-Chop is mastered, many surgeons feel more
comfortable transitioning to a full chop technique.
When sculpting the initial groove into the nucleus, it
is important to make a sufficiently long trench that ex-
tends from the sub-incisional region to the area under
the anterior capsular rim. The groove is deeper cen-
trally than peripherally, due to the natural shape of the
cataractous lens. The width of the groove should be
sufficient to allow placement of both the phaco tip as
well as the chopping instrument deep within the trench.
The initial phaco settings here should be a high pulse
mode (80 PPS or more), with a 40-60% duty cycle,
and a 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.
Once the instruments are placed deep within the trench,
and opposing forces can be gently applied so that the
nuclear halves are separated. Care should be taken to
separate centrally as well as peripherally in the groove
in order to get complete separation of the two halves.
If division is incomplete, then the individual nuclear
halves will not be easily chopped.
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%.
The fluidics must also be changed to increase the hold-
ing 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 cor-
responding higher bottle height to ensure that the in-
flow is greater than the outflo
in place, the phaco probe shou
nuclear half using ultrasound
pedal returned to position 2 wi
the nuclear half is stuck on th
to the iris plane, place the cho
the piece, and bring the two in
the chopper has cut through t
close proximity to the phaco
apart, towards the left and righ
segment. The first chopped seg
rated and the chopping steps r
both remaining nuclear halves
Stop-and-Chop is an importa
performing phaco chop. It’s
mastered by all surgeons, reg
prior experience. For those s
transition to a pure phaco ch
helpful to have Stop-and-Cho
nucleus removal.
Step 1.
Make a groove & crack
Allows more room for placement of the
phaco probe and second instrument
Make a Groove
Crack into Halves
Figure 1
LESSON 19
T
he technique of Stop-and-Chop uses a groov-
ing technique to make a single linear trench in
the cataract nucleus. The surgeon then stops,
divides it into two halves, and then chops each half fur-
ther. This is an easier transition for most surgeons and
results in more efficient surgery. Once the technique of
Stop-and-Chop is mastered, many surgeons feel more
comfortable transitioning to a full chop technique.
When sculpting the initial groove into the nucleus, it
is important to make a sufficiently long trench that ex-
tends from the sub-incisional region to the area under
the anterior capsular rim. The groove is deeper cen-
trally than peripherally, due to the natural shape of the
Once the instruments are placed deep within the trench,
and opposing forces can be gently applied so that the
nuclear halves are separated. Care should be taken to
separate centrally as well as peripherally in the groove
in order to get complete separation of the two halves.
If division is incomplete, then the individual nuclear
halves will not be easily chopped.
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
flow is greater than the outflow. To hold the nucleus
in place, the phaco probe should be embedded into the
nuclear half using ultrasound energy, and then the foot
pedal returned to position 2 with just vacuum. Now that
the nuclear half is stuck on the phaco tip, bring it up
to the iris plane, place the chopper around the edge of
the piece, and bring the two instruments together. Once
the chopper has cut through the nuclear half and is in
close proximity to the phaco tip, pull the instruments
apart, towards the left and right to separate the chopped
segment. The first chopped segment can be phaco-aspi-
rated and the chopping steps repeated to further break
Step 1.
Make a groove & crack
Allows more room for placement of the
phaco probe and second instrument
Step 2.
Now Chop Each Half
Figure 1
Figure 2

33. CENTRAL SAFE ZONE

34. THANKS