phaco machine, fluidics and dynamics
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PHACO MACHINE, FLUIDICS AND
DYNAMICSDr.Prathibha
Machine
Console, foot pedal and hand piece….with the connections
The console –computer based controls the functions of the machine
Settings of parameters flow rate, power, vacuum are preset and represent the maximum level that will be achievable during phaco by the surgeon
Multimodel panel diplay Memory button- surgeon setting saved
Hand piece
2 types- phaco and irrigation Phaco hand piece- piezoelectric
crystals(2-6)
Foot pedal
Central part and side clicks Controls the infusion, aspiration and the
phaco power 2dentations 3 excursions- I/IA/IAP Tactile feedback Auditory feedback
During the irrigation the pichvalve opens and irrigation is switched on- no pressure gradient:on/off
I dentation- nuclear rotation, manipulation of nuclear fragments, epinuclear plate etc..require irrigation with no aspiration
IA-irrigation +aspiration IAP excursion: the phaco energy intially zero -
>reach’s the preset level with foot pedal at the end of full excursion
The phaco energy delivery is linear in both surgeon mode(phaco1) and pulse mode(phaco 2)
Panel mode or the burst mode- energy is delivered as soon as the foot pedal is into IAP(step 3)
Side kick functions- Reflux button Vitrectomy Continuous infusion mode
Dynamic’s
The various functions of the the machine and it inter relationship with all parameters- dynamic’s
2 main functions of machine- emulsification- provides ultrasound energy and aspiration of the material…met with irrigation and aspiration
Irrigation aspiration- the parameter on which they depend is fluidics
Power Phaco needle movement creates mechanical power.
Total power is a combination of the frequency of the needle movement and stroke length. Power generation Produced in the hand piece by the ultrasound vibrations of piezoelectric crystals 2-6 in number.
Stroke length-Tip excursion or stroke length is defined as the distance the tip displaces in the longitudinal direction at maximum power. Stroke length varies for different machines and normally ranges from 1.5-3.75 mille-inches.
Frequency- 29-60KHz; most common 40KHz Each machine frequency is fixed…so power altered
with stroke length 2/1000-6/1000 of inch
Emulsification
Jack hammer effect Cavitation
Tips
Angulation-0-60 degree 60 0 ,450 ,300 , 150 and 00 More the angulation less the holding
power..more cutting power 30 and 45 deg tip preferred for divide and
conquer
Control and delivery of power
Surgeon mode/linear Panel mode Pulse mode Burst mode
Fluidics
Refers to the integrated functions performed by infusion and aspiration systems by which a stable AC is maintained
Advantage… closed chamber… maintaining a stable AC depth prevents damage to the cornea , iris and PC
Infusion system
Bottle with BSS…height of this creates a gradient for flow…gravity fed
The tubing from the bottle leads to a pinch valve which id controlled by the foot pedal
Gravity fed….2 feet= 44mmhg of pressure
Increasing the bottle height increases the flow and pressure- zonular stress…iris prolapse..miosis
Aspiration system
2 functions – lavage of AC and creation of hold for emulsification and crushing the fragments of nucleus
Lavage or clearing of AC is –flow rate governed
Hold is a function of vacuum Aspiration system has a Pump of the
machine flow based- peristaltic Vacuum based- venturi
Peristaltic pump
The rotation of the rollers by the pump pinches the soft silicon tubing's creating a negative pressure by squeezing the fluid out of the tube.
The faster the rollers rotate the higher the flow rate
The flow rate and the vacuum are set independently..the vacuum build’s up only after occlusion
Venturi pump
Flow rate
It determines how fast the things happen in the eye- cc/min
Vacuum
It is generated by the machine and is a measure of the strength of the hold that the hand piece has on the nucleus- holdability
Level of vacuum and port size determine the hold
Holding power is inversely proportional to the port size
Vacuum- nucleus,cortex,chopping,aspiration,I&A
Rise time
The time taken by a machine to reach the preset maximum vacuum after occlusion
In peristaltic depends on the vacuum after occlusion also on flow rate
In venturi- linear, fast and preset vacuum dependent not on flow rate
Central safe zone
Area within CCCPeripheral unsafe zoneCapsular fornices and angle region
Followability
Poitive presure of infusion and negative pressure of aspiration…create pressure gradient around the tip….eddy curren..area in the eddy current zone…zone of followabilty….tendency of the nuclear fragments th come into the tip
Area of highest followability in front of the tip…as go away from the tip no followabilty
References
Indian journal of ophthalmology:1997/45/issue4/page241-249
Textbook of ophthalmic surgery- Dr.Steinert
CME series- volume 21
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