Introduction to Phacodynamics

1. PHACODYNAMICS
PRESENTER: DR. IDDI NDYABAWE
MODULATOR: DR. LUSOBYA REBECCA

2. PHACODYNAMICS
• 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

4. Phaco machine
The machine consists of:
• the console,
• foot pedal,
• handpiece

6. CONSOLE
• Computer: hard and soft wares
• Generates U/S waves sent to
transducer as electrical signal
• Parameters fed in here: vacuum,
flow rates

7. FOOT PEDAL
• Foot pedal traverses is divided
by 2 dentations into 3
excursions-
1.) I (irrigation only),
2.) IA (infusion and aspiration) and
3.) IAP (infusion, aspiration and
phaco).

8. FOOT PEDAL
• essentially consists of main
central part and side kicks.
• The main part of the foot pedal
controls infusion, aspiration and
phaco power

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• Auditory and tactile feedbacks.
• Ability to move quickly from one mode to the other at the correct
time is the key to successful chopping.
• The point to remember is that in the I excursion, irrigation is fully on.
• In the IA excursion both irrigation and aspiration are on and in the IAP
excursion, irrigation is on, aspiration is at the maximum preset, and
phaco power will depend on the amount of depression

11. FOOT GRADIENT
• Foot gradient is the excursion of foot pedal in mm to produce unit
power of phaco energy.
• If the total foot excursion, from IAP0 to IAPmax is 10 cm i.e. 100mm
and the maximum preset phaco energy is 100%, then the foot
gradient (FG) becomes:

12. SIDE KICK FUNCTIONS
• The most important sidekick function of foot pedal is reflux.
• On kicking the side switch, aspiration flow rate is inverted and the material
aspirated is expelled into the 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.

13. TUBING
• Functions: irrigation and aspiration.
• Made up of silicon material which
can be autoclaved or ethylene
oxide (ETO) sterilized.
• Phaco fluidics depends upon the
quality of tubing.
• Factors: color, consistency, fittings

14. PHACO-PROBE
• It is a piezoelectric substance which converts electronic energy to mechanical
energy and thus giving the ultrasound energy under the influence of electrical
signal.
• Frequency: 30,000–60,000 Hz (Commonly used are 40,000 Hz).
• Different probes have different number of crystals ranging from 2-4.
• More the crystal the more is stroke length and more is the power
• PARTS
1. Phaco Handpiece
2. Irrigation aspiration handpiece
3. Phaco tip
4. Wrench

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• Functioning of the probe is to deliver the energy which cuts the hard
part of cataract which is the nucleus.
• The mechanism of working is by:
1. Jackhammer effect: It is the direct mechanical impact on the nucleus
to cut it.
2. Cavitational impact: With the gap between the phaco tip and the
nucleus the bubbles form in irrigating fluid in this gap which cuts the
tissue

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3. Acoustic wave of fluid: This is generated by the forward movement
of the tip, can disintegrate the lens material.
• Power of the machine depends upon the stroke length and the
frequency remains fixed

18. SLEEVE
• It is made of silicon material
which covers the phaco tip.
• It protects the cornea, iris from
transmitted heat energy by the
probe.
• The fluid for the irrigation flows
between the sleeve and phaco
tip thus cooling the tip

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• There are two openings 180° apart on the sleeve through which
irrigating fluid exit the sleeve.
• The size of the incision depends upon of tip gauge and the sleeve.
• The gauge of the phaco tip is fixed, but if you want to pass the phaco
tip by various lengths from 1.8 mm to 2.8 mm incision, it depends
upon the thickness of the sleeve.
• Many companies come with different color code for the various
thicknesses of sleeves

20. SLEEVE
• The distance between the distal end of the phaco tip and that of the sleeve
(exposed part of the phaco tip) defers from case to case.
• Hard cataract may need more exposed part of the tip and a softer cataract
may need a small exposed part of the tip.
• Direction of irrigation fluid flow depends upon the placement of the sleeve
over the phaco tip and this finally plays a very important role in phaco
fluidics.
• Sleeve is autoclaved or ETO sterilized

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22. TEST CHAMBER
• silicon-made
• for tuning of the machine and
before start of the case
• If a small nucleus particle is
stuck in the tip or aspiration
tubing, it can be removed in the
chamber with BSS solution in the
energy mode of the machine

23. PHACO WRENCH
• Phaco tip is screwed into the
handpiece by wrench

24. I – A tip
• The I-A tip differs from the
phaco tip in being smooth and
rounded with a single aspiration
port on the side of the tip and
not at the end.
• The aspirating port at one side
usually 0.75 mm to 1.5 mm away
from the tip.

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26. 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
• 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

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• 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. THE HIGHER THE
BOTTLE THE GREATER THE INFLOW
• OUTFLOW: vacuum, aspiration, tube sizing, incision architecture
• Aspiration Flow Rate: The amount of fluid flowing through the
tubing. This is reported in cubic centimeters per minute (cc/min).

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• 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
• Vacuum: after occlusion of phacotip by nuclear material how strongly
those material are held at tip. More vacuum -----more strong hold.

29. POWER
• Means change in stroke length..displayed 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

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• 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.

31. .
• 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

32. PHACOEMULSIFICATION POWER
VARIABLES
• The appropriate phaco power for a given surgical case is determined by three
variables:
1. The density of the nucleus
2. The amount of tip that is engaged
3. The linear velocity of the tip during emulsification
• Using less power would cause zonular stress, as the needle would push the
nucleus without smoothly sculpting it.
• Using more power would deliver more potentially damaging intraocular energy
without any beneficial effect.

33. DUTY CYCLE
• 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.

34. .
• MODERATE CATARACT: BH: 135cm, Power:40; Vacuum:275, Duty
cycle:40%, 30pps
• DENSE CATARACT: BH: 135cm, Power, Vacuum: 290, Duty cycle: 70%
with 70 pps
• Weak zonules: BH: 50-75, Power:40, entire diaphragm of capsular bag
tends to trampoline up and down, so goal is to stabilize the chamber.

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36. PUMPS
1. Diaphragmatic pump
2. Venturi pump
3. Peristaltic pump

37. PERISTALTIC PUMP

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39. DIFFERENCES

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42. RISE TIME
• The rise time is the time taken by a machine to reach maximum preset
vacuum after occlusion has been achieved.
• In a Venturi system, the RT is fast, linear and dependent upon the highest
preset vacuum, while in a peristaltic pump, RT depends on the FR of the
machine.
• The higher the FR, the lesser the RT though the relationship is not
absolutely linear

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