PHACODYNAMICS IN OPHTHALMOLOGY FOR BEGINNERS

SOURCES
1) Cataract surgery, Roger F Steinert, 3rd edition
2) A guide to phacoemulsification, Harbansh Lal, AIOS, CME series
3) Mastering the phacodynamics, Ashok Garg, 1st edition
4) Parsons’ Diseases of the Eye, 22nd Edition
1/7/20

SCOPE
1) Machine overview
•Console
•Handpeice
•Foot pedal
2) Fluidics
•Inflow and outflow
•Aspiration flow rate
•Vacuum
3) Vacuum pumps
4) Anterior chamber stability
•Compliance
•Surge
•venting
5) Ultrasonic power concept
•Phaco power
•Mechanism
•Control and delivery mode
•Phaco modes
6) Appropriate settings of
parameters

DEFINITION-
• Study of the fundamental principles
• inflow rates, outflow rates
• Vacuum
• phaco power modulation
• along with microsurgical maneuvers with
different types & grade of cataract.
• Logical setting --machine parameters in adaptation
to different surgical techniques.

History--
• Introduced by Charles D
Kelman in 1967
• Inspiration – dentistry
• Gold standard surgical
procedure for
management of cataract.

PHACODYNAMICS
 PHACO MACHINE OVERVIEW
 ULTRASOUND ENERGY
 FLUIDICS

PHACO MACHINE consists of the following parts-
1) A CONSOLE
2) The FOOT PEDAL
3) The HAND PIECE
& their connections.

CONSOLE-
 Computer –controls all
functions of the machine
 Settings for various parameters
• Power
• vacuum
• flow rate
 Multiple settings-- different
operating surgeons in same machine
 Input signals delivered --foot pedal
during procedure

HANDPIECE
Two types of handpiece
1) Phaco handpiece & 2) Irrigation aspiration handpiece.
Parts of a HANDPIECE---
- BODY
- ASPIRATION PORT
- PHACO NEEDLE
- SILICONE SLEEVE
- IRRIGATION PORT
- U/S PORT
Tip Irrigation(inflow) USG port Aspiration(outflow)
Sleeve Body

HANDPIECE
Body
Body-
• Contains piezo-electric crystals
• contract or expand on applying electric force
• converts electrical to mechanical energy
• causing movement of tip
• Crystals affected by temperature .
• Curie temperature--The point at which the crystal loses its
piezoelectric characteristics

HANDPIECE
SILICON SLEEVE for PHACOTIP-
1) Designed to insulate the corneal wound +
provide a fluidic pathway for irrigation.
2) Fluid insulation - important safety
mechanism to prevent excessive heating
of the region of the wound & corneal
burns.
Infusion fluid flows between the tip & sleeve
cooling the former.
2 openings on the sleeve is for exit of this
fluid, located perpendicular to the tip bevel.

HANDPIECE
Phaco Tip -
• Outer diameter – Wound size
• Inner diameter – aspiration flow Rate
• Inner diameter – holding ability
Phaco needle tip is made of
TITANIUM, covered with a silicon
sleeve .
Irrigation: 2 orifices located 180 deg.
apart on silicon sleeve
Inner diameter of tip can vary
- standard tips – 1.1mm & 0.9mm
- microtips – 0.9mm & 0.5-0.7mm

HANDPIECE
PHACO NEEDLE TIP -
1) A hollow titanium needle attached to the handpiece.
2) Angle at the end of standard tip range from 0 – 60 degree.
3) More the angulation (60 degree)
• lesser holding power
• cutting power is more.
4) Less angulated tips(15°and 0)
• better for holding
• poorer cutting action.
5) Tip selection depends on the hardness of nucleus &
technique.
6) 30 degree tip is a good compromise of these attributes, used
for both trenching & chopping.
7) End configurations can be round, ellipsoid, bent or flared.
Occludability:
- It is the tendency of the tip to get occluded
- Smaller tip angles have higher occludability

HANDPIECE
PHACO NEEDLE TIP----
Some advances in PHACOTIP with different purposes.
 To reduce incisional burns-
--- Microseal tip( Mc Kool)
--- Microflow tip
 To increase cutting efficiency-
---- KELMAN TIP
---- COBRA TIP

Irrigation – Aspiration Handpiece –
• Irrigation ports on the sleeve perpendicular to the
aspiration port
• Variety of I-A tips :
– Straight
– 45 degrees
– 90 degrees
– Flexible silicone tip
– Bimanual I/A

FOOTPEDAL
Consists of main central part & side kick.
CENRAL PART of foot pedal controls infusion, aspiration & phaco power.
2 dentations- D1,D2 & 3 excursions - I, IA & IAP
SIDE KICK has reflux function by inverting aspiration flow.

Excursion I - Irrigation only.
First dentation D1
Excursion IA - Irrigation + Aspiration (no US)
Second dentation D2
Excursion IAP - Irrigation + Aspiration + US.
 Resistance -- felt at dentations / positions where the mode changes on
depressing & while coming back up.
 Mandatory to be familiar with the feel of dentations of the pedal
(tactile feedback) & the sounds that machine makes (auditory feedback)
before attempting phacoemulsification.
 Ability to move quickly from one mode to other at the correct time is the key
to successful chopping.

Excursion I
 In excursion 1, pinch valve opens & irrigation is switched on.
 No gradient in this step & irrigation is either switched fully on or off
 As foot is brought back from IA/IAP excursion, stopping at this
dentation (D1) will keep on infusion, preventing collapse of AC.
 Steps like nuclear rotation, manipulation of nuclear fragments,
epinuclear plate etc. require a formed AC without any aspiration.

Excursion IA
Dentation 1 to dentation 2 is aspiration or IA excursion .
A linear control of vacuum & flow, so that the top
of foot position 2(IA excursion ) provides less
vacuum or flow than the middle or bottom range of
same foot position 2.(IA excursion )
To create vacuum & aspiration flow of
fluid, phaco machine must have a pump (
peristaltic or venturi pump)
2 primary sources of fluid outflow during
phacoemulsification
1) outflow from hand piece created by the
pump (aspiration tube)
&
2) leakage of fluid from the incisions.

Excursion IAP
 From dentation 2 to full depression is the phaco or ‘IAP’ excursion.
 At IAP0, phaco energy delivered will be zero and at IAP max , energy
will be maximum preset ,required for different types of cataract.
 Phaco energy delivery
 linear both in surgeon & pulse mode
 In panel or burst mode as soon as foot clear IAP0, maximum preset
energy is delivered.
In IAP excursion, Irrigation is on + Aspiration is at maximum preset +
Phaco power will depend on the amount of depression foot pedal.

Foot Gradient
Foot gradient is excursion of foot pedal in mm to produce unit power of
phaco energy.
Example—If the total foot excursion, from IAP0 to IAPmax is 10 cm i.e.
100mm and the maximum preset phaco energy is 100%, then foot
gradient (FG) become
FG = 100 mm /100 = 1 unit power per 1mm of excursions.
Now, if maximum preset phaco power is changed to 50%:
FG = 100mm / 50 = 1 unit power per 2 mm of excursion.
At phaco power 25% maximum:
FG = 100 mm / 25 = 1 unit power per 4 mm of excursion.
 Decreasing the maximum preset power on console increases the foot
gradient & hence the foot control.
 Phaco maximum should be set at the minimum power which is
required for a particular step in that grade of cataract.

SIDE KICK FUNCTIONS OF FOOT PEDAL
 Most important sidekick function of foot pedal is reflux.
 On kicking the side switch, AFR is inverted & the material aspirated is
expelled into AC.
 Since it is not a continuous function, for further reflux, the switch needs to
be kicked again.
 Inadvertent aspiration of wrong tissue (iris, capsule) can be released by
this function especially by beginners.

CONTINUOUS INFUSION MODE ( CIM )
- In this mode, the infusion remains on regardless of the position of the
Foot pedal i.e. even if the foot is accidentally lifted off ,the pedal the
infusion remains on, and the chamber remains formed).
-- Starts by kicking the side switch and remains on, till kicking the same switch
again stops it .
-- Boon for the inexperienced surgeon

Phacoemulsification: Fluidics concept
• Maintain Space
– Keep the eye inflated, prevent collapse of AC by maintaining a balance
between inflow and outflow rates
• Create Currents
– To bring cataract pieces to phaco probe
– To remove the cataract pieces
• Keep Things Cool
– To prevent thermal injury to the eye

PARAMETERS OF
FLUIDICS---
A. Mechanical Parameters
1. In Flow/ Infusion
2. Out Flow – Aspiration & Leakage
3. Vacuum
B. Clinical Parameters
1. Incision size
2. Vitreous Pressure

PARAMETERS OF FLUIDICS-
Flow of BSS from bottle to AC through irrigation port
Infusion is Passive by gravity
INFLOW / INFUSION Bottle height above the patient
creates a pressure gradient.
Approx. 11 mm Hg pressure (above ambient
atmospheric pressure) produced
intraocularly for every 15 cm (6 inches)
bottle height above patient’s eye.

Fluid leaves AC passing through phaco
needle into the aspiration tubing of handpiece,
OUT FLOW (cc/min; ml/min)
( Aspiration + Leakage )
Affected by Diameter of phaco tip,
Diameter of tubing , AFR, Vacuum
Another source of fluid loss is
through wound leakage.
PARAMETERS OF FLUIDICS

Amount of fluid flowing through the aspiration tubing.
Reported in cubic centimeters / minute(cc/min).
Flow is determined by speed of pump
As flow increases , current in AC increases +
determines how well particulate matter is attracted
to the tip
Optimum rate-20-36cc/min for most machines
ASPIRATION
FLOW RATE

FOLLOWABILITY---
– Tendency for structures
within the AC to move
towards the phaco tip
– It is a function of AFR
Positive pressure of infusion &
negative pressure of aspiration
creates pressure gradient at the tip
leads to eddy currents from the
infusion orifice to phacotip & this
area is known as zone of
followability.

VACUUM (mm Hg)-----
• Create holding power to keep material in phaco tip.
Vacuum is created by 2 types of pump---
• Peristaltic pump -- vacuum develops slowly
• Venturi pump – rapid rise in vacuum
• Trenching – low vacuum, no vacuum
• Segment removal – moderate vacuum
• Chop – high vacuum
Holdability – Ability of the phaco tip to hold onto the
material occluding its tip
– It is a function of Vacuum
.

ASPIRATION FLOW RATE AND VACUUM
• AFR is the rate at which fluid & emulsified nuclear particles
are removed from the eye when the phaco tip is unoccluded.
• Vacuum is the negative pressure that builds up when the tip
is occluded
• Vacuum and Aspiration are separate components that work
hand-in-hand during out flow.
• At low flow rates - Gradual build up of vacuum. Safer but
slower
• At high flow rates – vacuum build up fast . Faster but risky.

VACUUM PUMP
Part of the phaco machine which moves fluid through the aspiration tubing.
Pump settings control rate of movement of the fluid.
PUMPS are mainly of 2 types.
1) PERISTALTIC PUMP (Flow based) -
Allow independent control of both aspiration rate & vacuum level
2) VENTURI PUMP (Vacuum based) –
This pump type allows direct control of only vacuum level. Flow is
dependent upon the vacuum level setting.

Rollers while moving
compress the phaco outflow tubing in a peristaltic manner
physically moves fluid & creates a continuous “milking” action on fluid
column
phaco machine can directly control this flow level, hence the term flow
based
However, preset
vacuum level is
achieved once there
is occlusion of
outflow line i.e,at the
tip of phaconeedle
with cataractous
material.

PERISTALTIC PUMP contd.
 Vacuum not produced at low speeds of rotation unless the aspiration port
is occluded. As the speed of rotation is increased (by increasing flow
rate), vacuum is produced in the aspiration line without occlusion
 To built vacuum without occlusion , flow rate is to be increased & to
built vacuum at low flow rate occlusion of the tip is required.
SO CALLED AS FLOW BASED PUMP.

PERISTALTIC PUMP contd.
As the occlusion of phacotip by cataract 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

VENTURI PUMP (vacuum based)
 Vacuum level is created within a rigid drainage cassette, to which phaco
aspiration tubing is connected . As there is no milking of the aspiration
line, phaco tubing can be made rigid with low compliance.
 Advantage is the ablity to create the preset vacuum level without
occlusion of the phaco needle tip.
 As surgeon depresses the foot pedal, preset vacuum level is immediately
created, so the term vacuum based.
 As venturi & 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.

 In venturi pump Bernoulli’s principle is applied.
 The swift movement of a compressed gas creates a negative suction
force, i.e. the vacuum, inside a closed chamber.
 In a Venturi system, this principle is used to create vacuum in the
cassette (closed chamber). This vacuum is then directly transmitted to
the handpiece. The amount and speed of the gas decides the level of
vacuum developed in the cassette. This process is controlled by the foot
pedal.
A B
C

VENTURI PUMP
 In venturi system, only the level of vacuum can be controlled not the
flow rate
 Here the flow rate is a fixed fraction of the vacuum.
 The advantage of this system is that the vacuum is directly transmitted
to the tip from the system ensuring a better followability.

PERISTALTIC PUMP VENTURI PUMP
Flow based Vacuum based
Vacuum created only on Vacuum created instantly via
occlusion of phacotip by pump once surgeon press foot pedal
cataract material
No need of occlusion of phaco tip
Flow is constant until occlusion Flow varies with vacuum level
Drains into a soft bag drains into a rigid cassette.

 Peristaltic pump(slower flow rate) is useful for a beginner as it
provides more safety margin in the event of a sudden capsule
occlusion in the aspiration port.
 Slow rise time allows enough time for the surgeon to come back to
position 1 of the foot pedal or even relax.
 Disadvantage of peristaltic pump is due to longer procedure.
Peristaltic pump at a moderately high flow rate presents a good
compromise between safety & efficiency.

Other varieties of PUMPS
• Concentrix - Millennium
– Flow mode and Vacuum mode
• Rotary Vane – Chiron’s catalyst
– Vacuum-based system
• Diaphragm
– Vacuum-based

VACUUM --------RISE TIME
• The amount of time taken by the system to reach the maximum
vacuum setting once an occlusion takes place
• VTD have a much shorter rise time compared to peristaltic pumps
due to rapid flow rate.
 Peristaltic pump has a slower rise time, which can be made more
rapid by increasing rotation of the wheel (i.e. at higher flow rate).

CLINICAL PARAMETERS-
1. Incision size affects - Leakage
Infusion
Anterior chamber stability
Depend on external diameter of phaco tip
 Small incision causes Infusion flow obstruction leading to squeezing of
infusion sleeve in the event of tight wound. Leads to---
– Chamber instability
– Building up of heat at / around the tip
 Big incision  more leakage + more astigmatism.
2. Vitreous Pressure
• Patient dependent
• Affecting AC depth during phaco
• Could be compensated with increased bottle
height

ANTERIOR CHAMBER STABILITY
Anterior chamber stability is a condition where surgeons want to achieve
during phacoemulsification.
-- determined by fluid balance i.e, INLOW = OUTFLOW
-- To maintain chamber stability, the AC pressure has to be greater than
vitreous pressure & atmospheric pressure, i.e. positive IOP.
-- Achieved by adjusting fluidic parameters.
Inflow
outflow
Atmospheric pressure
Vitreous thrust

If inflow & outflow balance is altered, AC can be
under or over pressurized.
Under pressurization causes shallowing and / or
collapse of AC causing forward movement of
the iris + lens + posterior capsule leading to
FLUID inadvertent rupture of posterior capsule due to its
IMBALANCE movement towards the phaco needle.
One indicator of AC pressure imbalance is bouncing
movement of the iris & lens.
Over pressurization (bottle height too high) can cause
misdirection of aqueous fluid or deepening of AC
with zonular stress.

COMPLIANCE
Property of the tubing to collapse (deform under pressure) is the compliance of
the tubing.
Phaco needle tip occlusion,
Negative pressure will build in the tubing
leading to collapse of aspiration tube
COMPLIANCE
Occlusion breaks
Tube returns to original shape with temporary
fluid imbalance
SURGE
High compliance—more
surge
Low compliance--- less
surge

SURGE
Surge is the situation when the outflow fluid from the eye
exceeds the inflow fluid , even for just a fraction of a
second.
Phaco needle occluded by nucleus matter and tubing collapses due to
negative pressure.
Occlusion breaks after eating that nuclear piece
Negative pressure suddenly becomes off
Rate of fluid sucked into the phaco tube from AC can be temporarily
increased due to sudden expansion of the tubing.
Temporary shallowing until fluid is replaced by the infusion fluid.
( SURGE).

HOW TO REDUCE SURGE?
1) Lower levels of flow and vacuum
2) Rigid noncompliant aspiration tubing.
3) Venting.
4) Increasing bottle height
5) Reducing tip size

VENTING
The machine has got a sensor which detects occlusion break releases
fluid / air into the system to fill the volume of the re-expanding tubing,
preventing outlfow of fluid from AC.
Occlusion of phacotip by nuclear fragment
Vaccum created
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 vaccum from present level and no more
vaccum will be there beyond preset level (ADVANTAGE OF VENT)

Which vent is good????
Air or Fluid????
When Vaccum reached to preset level
Vent valve opens
Air or fluid enters the vacuum chamber ( air vent system/fluid vent system)……suppose stage 1
Bubbles of air/fluid expands but air expands more in vacuum in comparison to water bubble
stage 2
Once vacuum breaks( after emulsification of nuclear 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

MINIMIZING SURGE
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

CENTRAL SAFE ZONE –
---- This is not an anatomical area but a concept that needs to be understood
for performing safe aspiration.
---- This is an area within the CCC margin which is bounded vertically by the
cornea on the top and the posterior capsule in opposite direction.
---- This is the area with maximum space in the AC. All aspiration—nuclear,
epinuclear or cortical—can be done here with maximum safety .
CFZ
PERIPHERAL UNSAFE ZONE -- Due to the corneal curvature, as one
proceeds towards the periphery(capsular fornices and the angle region )one
enters an unsafe zone as there is less space for maneuvering. This constitutes
the Peripheral unsafe zone (PUSZ).

ULTRASONIC POWER CONCEPT :
Ultrasonic Power is the conversion of electrical energy into
mechanical one by ultrasonic vibrations of the Quartz crystal in
transducer / vibrator of handpiece.
Depends upon frequency(28-60 KHz) & Stroke length(2-6 million
thousandths of an inch).
More is frequency more is cutting action & more heat .
Longer the stroke length greater impact & heat generation.

PHACO POWER = STROKE LENGTH × FREQUENCY
Refers to number of longitudinal vibrations per second
FREQUENCY Commonest 40 KHz
of Fixed for a particular Phaco machine
HANDPIECE Usual range is 27- 60 KHz
Higher frequency – more efficient but more heat production
Distance the tip displaces in the axial direction during Phaco
STROKE
LENGTH Phaco power is altered by adjusting the stroke length.
Range is 1.5 – 3.75 mili thousandths of an inch.
Phaco power is indicated as a percentage. At phaco power of 100%, the
stroke length is the maximum permissible for that machine. When the power
is decreased by a given percentage, the stroke length also decreases.

TRANSDUCERS / ACOUSTIC VIBRATOR
PIEZOELECTRIC – U/S power generated by a piezo-electric crystal that
converts electric to mechanical energy.
- Crystals contracts or expands when electric force is
applied to it.
- Initial handpieces had 2 crystals.Newer phacomachines
use 4-6 crystal handpiece to improve reliability.
- The more the number of crystals,more is the stroke
length and hence more power i.e, 6 crystals give
more power than 2 crystals.
contd.

MAGNETORESTRICTIVE HANDPIECE-
- An externally applied magnetic field induces
lengthening / shortening of ferrite metal leading to linear
movement of the tip.
- The field may be applied by a direct current coil or a
separate permanent magnet.
- The lengthening effect decreases in magnitude with
increasing temperature.
- Less efficient & not popular any more.

MECHANISM OF PHACOEMULSIFICATION-
1. Jackhammer effect: physical striking of needle against nucleus by ‘to &
fro’ movement.
2. Cavitation effect: formation of microbubbles which at moment of
implosion increase temp. & shock wave
3. Acoustic wave: propagation of ultrasonic wave.

Phaco needle moving at ultrasonic speed
Creates intense zone of high and low pressure
Low pressure created withthe backward An equally intense zone of high pressure
movement of the tip, literally pulls created by forward movement of the
dissolved gases out of the solution phaco tip.
Microbubbles Compression of the micro bubbles
until they implode.
- At the moment of implosion, the bubbles create a temperature of 7204 degree
and a shock wave of 75,000 pounds per square inch (PSI).
- 75% of the micro bubbles implode, to create a powerful shock wave radiating
from the phaco tip in the direction of the bevel with annular spread.
- 25% of the bubbles are too large to implode. These micro bubbles are swept
up in the shock wave and radiate with it.

PHACO POWER VARIABLES
• Too little Power Pushes Nucleus instead of carving it Zonular
Stress/ Extension of PC tears
• Too much Power Pierces Nucleus Rent in PC
• Too much power Nucleus to fly away from the phaco tip resulting
in a CHATTER
• Safest phaco is performed not with low power but rather with
appropriate power
• Appropriate phaco power for a given surgical case depends on—
1.Density of the nucleus
2.Amount of the tip that is engaged
3.Linear velocity of the tip during Phacoemulsification

CONTROL & DELIVERY OF POWER -
SURGEON MODE / LINEAR MODE -
Progressive pressing of the foot-pedal
control leads to gradual rise in phaco
power from 0 to preset level.
PANEL MODE – Parameter reaches the preset panel
maximum on pressing the foot pedal
without any linear foot pedal control.
Linear mode preferred by most surgeons to control the power as
per the hardness of cataract.
Panel mode used in a very hard cataract with uniformly hard
nucleus requiring more or less uniformly high power for
emulsification.

PANEL MODE
SURGEON / LINEAR
MODE
Eg- IF PHACO POWER IS 70%,THEN PHACO
CAN BE DELIVERED AS………….
Different positions of FOOT PEDAL
70% all
throughout
0 to 70 % gradually

PHACO MODE
CONTINUOUS MODE –
Phaco power is delivered constantly and it can be
either linear or panel controlled.
PULSE MODE –
Phacopower is delivered as pulses of energy
followed by a gap of equal duration of pulse free
period.
BURST MODE –
Here maximum power is delivered at intervals which
vary with the amount of depression of foot pedal .

CONTINUOUS MODE-
All the time ultrasound is ON…….no OFF
In Every second……. all second is full with ultrasound
More USG power delivery as there is no gap
Uses—for sculpting .
PULSE MODE-
Phaco is not ON throughout all part of 1 second.
In 1 part of second phaco is ON and in another part of second phaco is
OFF….i.e, there is pause in ultrasound
1 sec 1 sec 1 sec 1 sec 1 sec 1 sec 1 sec
1 sec 1 sec 1 sec 1 sec 1 sec 1 sec 1 sec 1 sec

PULSE MODE-
 2 pulses per second-
1000/4 = 250 milli sec
125 1000/8 = 125 millisec
50
1000/20 = 50 millisec
50
250ms 250ms 250ms 250ms
125
50 % ON
&
50 %OFF
DUTY
Cycle
1 sec = 1000 millisecond

PULSES PER SECOND IN SURGEON / LINEAR MODE
U/S
POWER
Range of foot pedal in position 3
Eg- 2 pulses / sec,
Phaco power- 70 %
1sec

BURST MODE
2.5 sec
Burst width= 30- 500 millisec
U/S
50
LEVEL OF FOOT PEDAL IN RANGE OF POSITION 3

THUS,
IN CONTINUOS AND IN PULSE, PHACO ENERGY IS INCREASING
LINEARLY BUT NO LINEAR IN BRUST…THAT’S BURST.

HYPERPULSE
The concept of pulse and burst has been more modified in new
machine.
 Old machine had maximum pulse of 20 pps but new has upto 120 pps.
 Old machine had burst width as narrow as 30milisec whereas new has
4 ms.
 No change in the amount of phaco energy by using more pulses per
second because each short phaco pulse is followed by a short
phaco-off time.
 Duration of on and off time can also be decided by the operator, which is
called Duty cycle, thereby further reducing heat generation &
increasing followability.
Advantage of this upgraded range of programmability is the
smoothness & precision of power delivery.

DUTY CYCLE---
Newer machines has got softwares through which the surgeon can
even decide the duration of ontime & offtime thus reducing heat
generation & increasing followability.
PHACO ON TIME
DUTY CYCLE = -------------------------------------------------------------
PHACO ON TIME + PHACO OFF TIME
Duty Cycle---time during which power is on as % of cycle (traditionally 50%)
i.e 50% time USG ON…50% OFF
DUTY CYCLE can be changed or modified.
Duty cycle 50%... .means 50% time USG on…50% time no USG
Duty cycle 20%---- 20% time Phaco ON…80% time OFF

CHANGE IN DUTY CYCLE
-- Higher duty cycle results in better cutting power but increased heat generation
-- Lower duty cycle allows more fluidic aspiration of nuclear fragments while
minimizing heat and phaco power

USES OF PULSE MODE
To hold lens eg.– CHOPPING
or
Bringing material to central
area
-- SCULPTING
-- To remove quadrants
2 Pulses / second 8 Pulses / second

USES OF BURST MODE
For
epinucleus
removal
To hold lens eg.-
Chopping or to
bring material to
central area.
To remove the
quadrants
Sculpting

APPROPIATE SETTINGS
OF PARAMETERS

SETTINGS AT DIFFERENT PHASES
STEP PRINCIPLE AFR
( cc/min )
VACUUM
( mmHg )
POWER
( % )
TRENCHING High Power
Low Vacuum
20-25 0-15 60-70%
CHOPPING High Vacuum
Mod Power
25-30 100-200 50-60%
QUADRANT
REMOVAL
High Vacuum
Mod power
25-30 100 50%
EPINUCLEUS
REMOVAL
High Vacuum
No / low
phaco
30-35 70-100 40 %
CORTEX
ASPIRATION
High vacuum 25-30 400 N/A

CONCLUSION
 A thorough understanding of fluidics is very
critical for safe and efficient use of the technology.
 Proper knowledge about the machine setup is essential
for its functioning and also to get the maximum
advantages of its capabilities.
 The machine should always be checked before
operation for a smooth surgery.

PHACO POWER DELIVARY
MODES
• Traditionally -- longitudinal manner --forward and back
• Recent innovations -- Lateral motion
• Lateral motion --Increases cutting efficiency by reducing
repulsion of lens material
• 2 types of lateral motion
• torsional-- phaco tip oscillates in a rotational manner
along its primary axis
• transversal--phaco tip moves in an elliptical path
1/7/20

• Conventional US mode – longitudinal
phacoemulsification – produce repulsion effect --
phaco tip pushes the nucleus away with each stroke
as it moves forward
• Thus, the US is interrupted and efficiency of
phacoemulsification is compromised
1/7/20

NEOSONIX- TORSIONAL
PHACO
• January 2006, Alcon Surgical incorporated OZil
torsional into the Infiniti Vision System
• Hardware and software upgrade of the machine
• Dedicated hand-piece that produces rotary
oscillations of the phacoemulsification tip with a
frequency of 32 KHz
• Does not produce repulsion and breaks up cataract
by shearing and not by conventional jackhammer
effect
1/7/20

Shaft of the torsional hand-piece oscillates
side-to-side movement at the tip
angulated tips -- motion of thetip within the nuclear tissue
is up to three times greater than movement of the tip’s
shaft
1/7/20

“U/S AVE”- Ultrasound average
• Percentage of maximum
“EPT” - elapsed phaco time
• The total time during which phaco ultrasonic power
was delivered
“APT” - Absolute phaco time
• total energy delivered into the eye
APT = “U/S AVE” X “EPT
1/7/20

• Same energy delivered:
• 15 seconds of 100% power
1/7/20

Other modalities
• Laser lens ablation-
• Nd:YAG laser
• invented by Jack Dodick,
• very similar to ultrasonic phacoemulsification --without
the vibrating probe and its attendant thermal
complications
• The probe is smaller and focuses its laser energy on
a titanium target at the end of the probe.
• Causes shock waves to emanate from the tip
facilitating acoustic breakdown of lens material.
• Inefficient at removing denser cataracts.
1/7/20

• Erbium:YAG laser-- (wavelength of 2940),
• Employed by the Ascelepion-Meditec Phacolase unit
• emits energy from a smooth distal tip resulting in
photoacoustic breakdown of lens material
• The absorption of erbium laser is 1000 times greater
than that of the Nd:YAG laser
• reducing thermal scatter and confining the energy to
the immediate vicinity of the tip.
1/7/20

• Aqualase (Alcon Infiniti)
• Achieves emulsification via a deflected stream of
warmed BSS that is ejected from the tip.
• In both aqualase and other laser modalities,
emulsifying energy is emitted from the tip, rather than
the tip itself having emulsifying properties as in
phacoemulsification
• Alex Urich invented the STAAR sonic wave handpiece
which drives the ultrasonic needle at a much lower
frequency (40 to 400 Hz, compared with the ultrasonic
frequency of >20,000 Hz), thus eliminating thermal injury.
1/7/20

PHACODYNAMICS IN OPHTHALMOLOGY FOR BEGINNERS

Recommended

Recommended

More Related Content

Similar to PHACODYNAMICS IN OPHTHALMOLOGY FOR BEGINNERS

Similar to PHACODYNAMICS IN OPHTHALMOLOGY FOR BEGINNERS (20)

Recently uploaded

Recently uploaded (20)

PHACODYNAMICS IN OPHTHALMOLOGY FOR BEGINNERS