Phaco Machine, Fluidics and Dynamics

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