phacoemulsification technology power and fluidics

1. Phacoemulsification
Technology
Power and Fluidics
M.Khanlari, MD

2. Introduction
Phacoemulsification can be described
based on two fundamental components
 Ultrasound Energy (Power)
 Fluidics Circuit

3. Phacoemulsification
Technology
Power

4.  All phacoemulsification machines consist of
 A computer to generate ultrasonic impulses
 A transducer
 Piezo electric crystals that turn these electronic
signals into mechanical energy
 The energy that is created is then harnessed within
the eye to overcome the inertia of the lens and
emulsify it
 Once turned into emulsate, the fluidics system removes
the emulsate, replacing it with balanced salt solution.

5.  Power is created by the interaction of
frequency and stroke length

6. Frequency
 The speed of the needle movement
 Determined by the manufacturer of the machine. Presently,
most machines operate at a frequency of between 35,000 to
45,000 cycles per second (Hz)
 As the resistance to the phaco tip varies, small alterations in
frequency are created by the tuning circuitry in the computer
to maintain maximum efficiency
 The surgeon will subjectively appreciate good tuning circuitry
by a sense of smoothness and power.

7. Stroke length
 The length of the needle movement
 This length is generally 2 mils (thousandths of an inch) to 6 mils.
Most machines operate in the 2-mil to 4-mil range
 Longer stroke lengths are prone
 to generate excess heat
 the greater the physical impact on the nucleus
 the greater the generation of cavitation forces
 Stroke length is determined by foot pedal excursion in position 3
during linear control of phaco.

8. Energy at the Phaco Tip
 The actual tangible forces that emulsify the
nucleus are a blend of the "jackhammer"
effect and cavitation

9. The jackhammer effect
 Is merely the physical striking of the
needle against the nucleus.

10. The cavitation effect
 The phaco needle creates intense zones of high and low pressure
 Low pressure, created with the backward movement of the tip, literally pulls
dissolved gases out of the solution, thus giving rise to micro bubbles
 Forward tip movement then creates an equally intense zone of high pressure. This
produces compression of the micro bubbles until they implode.
 At the moment of implosion, the bubbles create a temperature of 13000° F and a
shock wave of 75,000 pounds per square inch (PSI)
 Of the micro bubbles created, 75% implode, amassing to create a powerful shock
wave radiating from the phaco tip in the direction of the bevel with annular spread.
However, 25% of the bubbles are too large to implode. These micro bubbles are
swept up in the shock wave and radiate with it.
 The cavitation energy that is created can be directed in any desired direction; the
angle of the bevel of the phaco needle governs the direction of the generation of
the shock wave and micro bubbles.

11.  Emulsification is most efficient when both the jackhammer
effect and cavitation energy are integrated
 To accomplish this, a 0° tip, or the bevel of the needle,
should be turned toward the nucleus or nuclear fragment.
 This maneuver will cause the broad bevel of the needle
to strike the nucleus, which will enhance the physical
force of the needle striking the nucleus.

12.  The cavitation force is then concentrated into
the nucleus rather than away from it This
causes the energy to emulsify the nucleus and
be absorbed by it
 When the bevel is turned away from the
nucleus, the cavitational energy is directed up
and away from the nucleus toward the iris and
endothelium
 Finally, in this configuration, the vacuum force
can be maximally exploited as occlusion is
encouraged

13. Thirty-degree tip

14. Zero-degree tip

15. Modification of Phaco Power Intensity
 Unnecessary power intensity is a cause of heat with subsequent
wound burn, endothelial cell damage, and iris damage with
alteration of the blood-aqueous barrier
 Phaco power intensity can be modified by alteration in
 Stroke length
 Duration
 Emission

16. Alteration of Stroke Length
 Determined by foot pedal adjustment
 In linear phaco, depression of the foot pedal will increase
stroke length and, therefore, power
 Foot pedals (Sovereign and the Legacy )permit surgeon
adjustment of the throw length of the pedal in position
3.This can refine power application
 The Millennium dual linear foot pedal permits the
separation of the fluidic aspects of the foot pedal from the
power elements

17. Power Phases
 All of the power modes are essentially
combinations of phaco-on periods
followed by phaco-off periods.
 The % of phaco-on time to total time (on
+ off) is called the duty cycle.

18. Power Modes
 Continuous
 US power applications, at infinitely small rest
 More pedal depressed, higher phaco power( linear control of power )
 Pulse mode
 Variable US power to be applied, at a fixed rest
 More foot pedal depressed, powerfull pulses with fixed rest (linear control
of phaco power )
 The total energy delivered is cut in half as compared with the continuous
mode
 Burst mode
 Fixed US power applications, at variable (rest)
 More foot pedal depressed, shorter rest (fixed nonlinear control of power )
 With maximum foot pedal depression same as continuous mode

20. Alteration of Emission
Modified by tip selection. Phaco tips can be modified to
accentuate power, flow, or a combination of both
 Power intensity is modified by altering the bevel tip angle
 Kelman tip
 Flare and cobra tips
 Flow rate is modified by
 Smaller diameter tips, such as 21-gauge tips.
 Microseal tips
 Accentuation of power and flow
 Alcon ABS (aspiration bypass system) tip

21. Phacoemulsification
Technology
Fluidics

22. Fluidic Circuit
 The phaco tip must operate in a cool environment
and with adequate space to isolate its actions from
delicate intraocular structures. This portion of the
action of the machine is dependent upon its
fluidics

23. Fluidic Circuit
 Used to remove the emulsate while
maintaining the anterior chamber
 Supplied by an elevated irrigation bottle to
maintain the chamber hydrodynamically (fluid
volume) and hydrostatically ( fluid pressure)
 Regulated by a pump

24. Fluidics
The fluidics of all phaco machines are
fundamentally a balance of fluid inflow and
outflow

25. Inflow
 Inflow is determined by the bottle height above
the eye of the patient. It is important to recognize
that with recent acceptance of temporal surgical
approaches, the eye of the patient may be
physically higher than in the past. This requires
that the irrigation bottle be adequately elevated. A
shallow, unstable anterior chamber will otherwise
result.

26. Outflow
 Outflow is determined by the
 Sleeve-incision relationship
○ The incision length selected should create a snug fit with the phaco tip selected.This will
result in minimal uncontrolled wound outflow with resultant increased anterior chamber
stability
 Aspiration rate or flow
○ Is defined as the flow of fluid through the tubing in cubic centimeters per minute (cc/min).
With a peristaltic pump, flow is determined by the speed of the pump. Flow determines
how well particulate matter is attracted to the phaco tip
 Aspiration level or vacuum
○ is a parameter measured in millimeters of Mercury (mm Hg) that isdefined as the
magnitude of negative pressure created in the tubing .Vacuum is the determinant of how
well, once occluded on the phaco tip,particulate material will be held to the tip.

27. Vacuum Sources
There are three categories of vacuum
sources, or pumps
Flow pump
Vacuum pump
Hybrid pump

28. Vacuum Sources
 Flow Pump
 The primary example of the flow pump type 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.
Additional examples are the rotary vane and diaphragmatic pumps
 Hybrid Pump
 The primary example of the hybrid pump is the Sovereign peristaltic pump or the Concentrix pump
(Bausch & Lomb Surgical) These pumps are interesting in that they are able to act as either a
vacuum or flow pump dependent upon programming. They are the most recent supplement pump
types and are generally controlled by digital inputs, creating incredible flexibility and
responsiveness.

29. Pump
 Clears the chamber of emulsate , and also
provides significant clinical utility
 When the tip is unoccluded , produces current in
the AC (cc or ml per min) which attract nuclear
fragment
 When the tip is occluded ,provides holding
power or vacuum (mmHg) , which grips the
fragment

30. Flow pump
 With a flow pump , a surgeon commands a
given flow rate while vacuum varies to a point
that is also surgeon selected

31. Flow pump
 Surgeon may command an aspiration flow rate
(cc/min or ml/min)
 Surgeon sets a vacuum limit (mmHg) , the
point at which the machine stops building
vacuum by sufficient fluid resistance
 Regulates the fluid in aspiration line via direct
contact between the fluid and the pump
mechanism
 May use a collapsible drainage pouch or scroll
pump (Millennium , Concentrix )

33. Flow pump
 Aspiration flow rate is directly proportional to
the rotation speed of the pump (rpm)
 Regulates the flow rate independently of the
amount of pressure in the line via the elevated
irrigating bottle
 Regardless of the pump type , actual
aspiration flow rate depends on the degree of
tip occlusion

34. Rise time
The amount of time required to reach a
given vacuum preset , assuming
complete tip occlusion
 Inversely proportional to the rotational
speed of the head
 A longer rise time →more time to react in
cases of inadvertent incarceration of ocular
tissues

35. Rise time

36. Vacuum pump
A surgeon commands a given vacuum
that it indirectly controls flow rate

37. Vacuum pump
 A surgeon is unable to directly controls flow
rate
 A surgeon directly commands the actual
vacuum level (not a limit )
 Usually indirectly linked to the fluid in the
aspiration line via their drainage cassette that
is between the pump and the aspiration line
 Rigid cassette or pouch versus flexible
drainage pouch used with flow pump

38. Vacuum pump
 When the tip is occluded , flow ceases and
vacuum is transferred from the cassette down
the aspiration line to the occluded tip
 Rigid cassette and tubing versus rollers and
collapsible tubing inflow pump results in less
compliance
 Lower compliance and shorter time for
vacuum transfer results in typically lower rise
time versus flow pump
 Lower rise time can be a potential liability if
unwanted material incarcerated in aspiration
port (Exception : Millennium,…)

39. Advanced Power Modulations
 Pulse and burst Settings
Hyperpulse
Hyperburst or micro-burst
linear burst
Time off limited linear burst
 Duty Cycle
 Variable Rise Time
 Occlusion mode

40. Hyperpulse and hyperburst
 Hyperpulse
 Increased pulses to as many as 120 pulses/s instead of 20 pulses/s in the
traditional pulse mode
 It reduces heat without change the total energy because each pulse is
immediately followed by a brief rest.
 Also increases the effectiveness of cutting, when a very high rate (eg, 120
pulses/s) is used.
 Hyperburst or Microburst
 The minimum microburst of energy can be programmed as low as 4 millis
instead of 80 millis in traditional burst mode
 This ability affords delivery of smaller bursts of phaco energy and thereby
minimizes the build-up of heat and the total phaco energy used

41. Linear burst (vs nonlinear)
 As the pedal is pressed, power increases, but bursts
also come closer together. At maximum
travel the phaco becomes continuous

42. Time off limited linear burst phaco
 Similar to linear burst, but a lower limit to
the off-time has been set, so it never
becomes continuous

43. Variable Rise Time
 Burst and pulse modes deliver square-wave energy by default, which means
 the power goes from zero to the preset level immediately and the
resulting waveform on the oscilloscope looks like a square.
 With a variable rise time, we can have the phaco energy ramp up over the
course of each individual pulse or burst, resulting in a ramped wave

44. Variable Rise Time
 This allows
 Better followability
 Less chatter
 Less energy and less heat
 This gradual ramping up of power achieves a “pulsed pulses” effect.
 when the pulse width or burst width is so short that there is insufficient time to fully
ramp up each packet of phaco energy it is difficult to use a variable rise time

45. Occlusion mode
 This technology, currently available only with the peristaltic
pump (not the Millennium’s venturi pump),
 Allows the application of different phaco settings before and
after tip occlusion.
 For example:
○ if the vacuum level is 325mmHg, the surgeon can set a threshold
vacuum level of 250mmHg, when tip occluded
 Typically, postocclusion settings should have a higher duty
cycle, a higher maximum power, and a lower aspiration flow
rate
 For example
○ power increases from 35% to 45%, duty cycle increases from CL
(20%) to CD (43%) and aspiration flow is decreased from 30 to
24mL/min.

46.  With proper modification of power
intensity and choosing the proper mode
we have
Efficient emulsification and
Less complication
○ Corneal burn
○ Endothelial cell damage
○ Iris damage
○ Alteration of the blood-aqueous barrier
○ …

47. Phaco technique
 To appropriately adjust the machine
parameters for various stages of surgery , it is
necessary to analyze the function of those
parameters for a given stage and for a given
pump type

48. Phaco technique
sculpting
Require
 titration of power
 enough flow to clear the anterior chamber of
the emulsate
 Sufficient flow to cool the phaco tip
flow pump :flow rate 20-25 cc/min
vacuum pump:vacuum 30-50 mmHg

49. Divide-and-Conquer Phaco
Sculpting
 To focus cavitation energy into the nucleus, a 0°, 15°, or 30° tip
turned bevel down should be use
 Zero or low vacuum is mandatory for bevel down phaco to
prevent occlusion.
 Occlusion, at best, will cause excessive movement of the
nucleus during sculpting. At worst, occlusion is the cause of
tears in capsular bag
 Once the groove is judged to be adequately deep, the bevel of
the tip should be rotated to the bevel up position to improve
visibility and prevent the possibility of phaco through the
posterior nucleus and capsule.

50. Divide-and-Conquer Phaco
Quadrant and Fragment Removal
 Vacuum and flow are increased to reasonable limits
subject to the machine being used. The limiting factor to
these levels is the development of surge
 The bevel of the tip is turned toward the quadrant or
fragment, and low pulsed or burst power is applied at a
level high enough to emulsify the fragment without driving
it from the phaco tip
 Chatter is defined as a fragment bouncing from the phaco
tip due to aggressive application of phaco energy

51. Divide-and-Conquer Phaco
Epinucleus and Cortex Removal
 The vacuum is decreased while flow is maintained. This
allows for grasping of the epinucleus to the anterior capsule.
The low vacuum will help the tip hold the epinucleus on the
phaco tip without breaking off chunks due to high vacuum,
so that it scrolls around the equator and can be pulled to the
level of the iris
 Here, low-power pulsed phaco is used for emulsification
 If cortical cleaving hydrodissection has been performed, the
cortex will be removed concurrently

52. Stop and Chop Phaco
Chopping and Cracking
 After Groove creation the phaco tip and chopper are placed in
the depth of the groove and separated, creating a crack
 Vacuum and flow are increased to improve the holding ability of
the phaco tip. The nucleus is rotated 90°, the tip is then
burrowed into the mass of one heminucleus using pulsed linear
phaco
 Excessive phaco energy application is to be avoided, because
this will cause nuclear material immediately adjacent to the tip
to be emulsified
 With a good seal, the heminucleus can be drawn toward the
incision, and the chopper can be inserted at the
endonucleus/epinucleus junction

53. Phaco Chop
 The phaco chop requires no sculpting. Therefore, the procedure is
initiated with high vacuum(>100) and flow(30-35 cc/min) and linear
pulsed phaco power.
 For a 0° tip, when emulsifying a hard nucleus, a small trough may
be required to create adequate room for the phaco tip to borrow
deep into the nucleus
 For a 15° or 30° tip, the tip should be rotated bevel down, to
engage the nucleus
 A few bursts, or pulses, of phaco energy will allow the tip to be
buried within the nucleus. It then can be drawn toward the incision
to allow the chopper access to the endonucleus/epinucleus
junction
 There, it is emulsified with low linear power, high vacuum, and
moderate flow.

54. Phaco Technique
Chopping
Horizontal chopping (Nagahara originial
method)
 Actual chop require only moderate vacuum due to
mechanically fixation between tip and chopper
 Gripping and manipulating the fragment require
higher vacuum levels of 200 mmHg to 250

55. Phaco Technique
Chopping
Vertical chopping (Phaco crack, Quick chop, Snap
and Slit)
 Actual chop require a higher vacuum
setting due to unfixated nucleus between
tip and chopper

56. Irrigation and Aspiration
 Similar to phaco, anterior chamber stability
during irrigation and aspiration (I&A) is due to
a balance of inflow and outflow
 There, in the safety of a deep anterior
chamber, the vacuum can be increased and
the cortex aspirated
 Generally, a 0.3-mm I&A tip is used. With this
orifice, a vacuum up to 500 mm Hg and flow of
20 cc/min is excellent to tease cortex from the
fornices.

57. Surge
 Occurs when an occluded fragment is
held by high vacuum and is then
abruptly aspirated (with a burst of
ultrasound) ,fluid tends to rush into the
tip to equilibrate the built up of vacuum
in the aspiration line and potentially
consequential shallowing or collapse of
the anterior chamber

58. Surge
Methods to combat surge
 Fluidic circuits are engineered with
minimal compliance (peristaltic pump)
 A second higher irrigating bottle
 Vacuum sensing feedback loop via
microprocessor control
 Small bore aspioration line tubing
(Micoflow needle)

59. Surge Modification
 The following are some examples of new
technologies
 Sovereign - At the moment of surge, the
machine's computer senses the increase in
flow and instantaneously slows or reverses the
pump to stop surge production.
 Millennium - The dual linear foot pedal can be
programmed to separate both the flow and
vacuum from power.
 Legacy - The ABS tips. During occlusion, the
hole provides for a continuous alternate fluid
flow

61. Flow pump50
 In spite of complete occlusion of tip , a minute
amount of fluid is pumped from the aspiration
line tubing as vacuum is built up, thus
accounting for the relationship of pump speed
to rise time

62. Flow pump51
Two factors account for this relationship
 Slippage between the pump rollers and the
tubing and between the opposed internal
surfaces of the aspiration line tubing
 Enough aspiration line tubing compliance to
allow for collapse by the pump rollers

63. Flow pump52
A variety of methods can be used to
prevent vacuum built up past this level
 Stopping the pump head when the
preset value is reached
 With a moving pump head, venting air or
fluid into the aspiration line when the
preset value is reached

65.  A solution to this issue is the Dual linear
foot control of the Millennium

67. 60
 Direct linear control of vacuum has another
advantages with vacuum pumps in that it
allows subsequently indirect linear control of
aspiration flow rate when the tip aspiration
port is unoccluded.

77. Alteration of Duration
 Pulse mode provides for an added margin of safety and a
deeper anterior chamber to work within
 This occurs because each period of phaco energy is
followed by an interval of no energy
 In pulse mode during the interval of absence of energy,
the epinucleus is drawn toward the phaco tip, producing
occlusion and interrupting outflow
 This allows inflow to deepen the anterior chamber
immediately prior to the onset of another pulse of phaco
energy

78.  BURST MODE
Single burst
Multiple burst
 PULSE MODE
Short pulse
Long pulse