PHACO Basics

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PHACO Basics::

PHACO Basics: Instrumentation Dr.Kaivan Shah Dr.Ronnie J.George

IT CAN BE DIVIDED UNDER 2 TOPICS: :

IT CAN BE DIVIDED UNDER 2 TOPICS: 1.PHACOMACHINE & 2.PHACODYNAMICS

PHACOMACHINE :

PHACOMACHINE The machine consists of the console, foot pedal, handpiece and their connections. CONSOLE The console consists of a computer which controls all the functions of the machine. The settings for the various parameters, i.e. power, vacuum and flow rate are fed in here. Multiple of such settings can be stored in memory for different operating surgeons in same machine. Input signals are delivered from foot pedal during procedure by changing its position and selecting mode.

2. HANDPIECE :

2. HANDPIECE There are two types of handpiece Phaco handpiece & Irrigation aspiration handpiece . Phaco handpiece contains the piezoelectric crystal which in contact with titanium tip. Tip is covered by a silicon sleeve. It is connected to the console with an electric cord. There are two more connections: one each for the irrigation tubing and for connecting the aspiration system.

3. FOOT PEDAL:

3. FOOT PEDAL Consists of main central part & side kick. Cenral part of the foot pedal controls infusion, aspiration and phaco power. 2 feedbacks- tactile & auditory 2 dentations & 3 excursions-I, Ia & Iap Side kick has reflex function by inverting aspiration flow.

PowerPoint Presentation:

FOOT PEDAL FUNCTION 0 - Resting FOOTSWITCH 3 - Irrigation+Aspiration + Phacoemulsification 2 - Irrigation+Aspiration 1 - Irrigation 97/3421

PHACODYNAMICS:

PHACODYNAMICS 2 components: Ultrasonic power & Fluidic system. Ultrasonic power: Mechanism: conversion of electrical energy into mechanical one by Ultrasonic vibrations of the Quartz crystal in transducer Depends upon frequency(29-60Hz) & Stroke length(2-6mils) More is frequency more is cutting action & more heat Longer the stroke length greater impact & heat generation. Frequency is constant for each machine,but stroke length is variable depending on foot pedal excursion.

TRANSDUCERS :

TRANSDUCERS Piezoelectric – reversal of piezoelectric phenomenon advantage : - high efficiency – less heat production disadvantage : - shorter life Magnetostrictive advantage : - contact free excitation, long life span disadvantage : - low efficiency – high heat production, tissue burn

Mechanism of emulsification: :

Mechanism of emulsification : Jackhammer effect : physical striking of needle against nucleus by ‘to & fro’ movement.[transverse in Ozil & elliptical in Eclipse machine] Cavitation effect : formation of microbubbles which at moment of explosion create 7204’c temp. & shock wave of 75000psi which can be directed away from cornea according to angle of tip.

PHACO TIPS:

PHACO TIPS Titanium Tip is covered with a sleeve that insulates & protects the sclero -corneal tissue from thermal & mechanical damage Irrigation: 2 orifices located 180 deg. apart on silicon sleeve Diameter of tip can vary - standard tips – 1.1mm & 0.9mm - microtips – 0.9mm & 05-0.7mm available in different angulation : 0,15,30,45 & 60 deg. More is angle,more cutting action but less holding & vice versa.

SLEEVE:

SLEEVE 1.Rigid : - Material : Polysulfon , teflon - ADV.- Continuous inflow, no wound burn - DISADV.- Difficulty in manipulation 2.Flexible : - Material : Silicone - ADV.- Conforms well with inner incision- minimal wound leak -DISADV.- Can be compressed during surgery –chamber collapse,wound burn 3.Storz microseal tip: Dual infusion sleeve surrounding the titanium needle Outer :flexible silicone Inner :rigid sleeve

I/A HANDPIECE:

I/A HANDPIECE Differs from phaco tip being smooth and rounded with a single aspirating port on the side of the tip, not at the end. Diameter of tip - 0.2 & .5 mm. With sleeve total diameters is 2mm. Straight, 45° degree, 90° tips are available.

Modes of phaco energy::

Modes of phaco energy: Linear vs Panel mode. Pulse(0-12) vs Burst mode. Hyperpulse –pulses in hundreds or thousands in newer phaco machines. Duty cycle

2.Phacofluidics: :

2. Phacofluidics: refers to integrated functioning of infusion & aspiration system to maintain stable A/C by balancing input & output from A/C. Input equals Irrigation fluid & output to AFR+leakage from wound site. 1. Infusion system : consists of a bottle , the height of which provides the gradient for flow & irrigation tube Infusion is gravity fed, 2 feet bottle height conforming to approximately 44 mmHg.(safe limit:3+/-2) In order to obtain constant pressure, bottle is positioned at certain height and the same amount of liquid is aspirated by the pump at steady rate Too high bottle results in zonular stress,repeated lens-iris fluctuation & miosis,iris prolapse if small pupil & large wound.

Infusion(cont.):

Infusion(cont.)

2.Aspiration system:

2. Aspiration system Function of this is lavage of the A/C governed by flow rate and creation of a hold for emulsification of the nucleus provided by vacuum. Flow pumps - peristaltic - scroll Vacuum pumps - venturi - diaphragm - rotary vane

PowerPoint Presentation:

PERISTALTIC PUMP :(flow based) These are designed with the rollers over which tubing is stretched and locked in place. As the rollers of the pump gently roll over the tubing, compression waves are created that push a specific amount of fluid away from the hand piece. This creates a negative pressure in the aspirating tubing which depending on the level draws fluid out of the eye. The continued rotation creates a pressure differential and as the aspirating port is occluded by the nucleus, vacuum is produced in the aspirating tubing.

2. VENTURI PUMP (vacuum based):

2. VENTURI PUMP (vacuum based) It is driven by the compressed gas which generates vacuum. This vacuum produced is related to the flow of gas which is regulated by a valve. Difference in this pump and peristaltic pump is that here vacuum built is almost instantaneous from zero to preset level on pressing the foot pedal. As a result of rapid rise in vacuum with this pump, there is increased risk of posterior capsular rupture. In this, only the level of vacuum can be controlled and not the flow rate c.f. in peristaltic, vacuum & flow can be controlled independently. Only advantage is better followability .

ASPIRATION FLOW RATE::

ASPIRATION FLOW RATE : It refers to the volume of fluid removed from the eye in ml/min. High AFR needs bottle height should be elevated to compensate for increased fluid loss, Flow rate affects the speed with which the material is attracted to the ultrasound or irrigation/aspiration tip. High AFR results in attraction of lens material towards phaco tip like magnet called followability with faster vacuum build up and swifter removal of lens matter but with less power Optimum rate-20-36cc/min for most machines.

Vacuum::

Vacuum : Vacuum is the suction force created by the pump at the phaco tip. It serves to hold the nucleus pieces in apposition with the phaco tip, facilitating their removal. In the system fitted with an aspiration pump it is the pressure difference that attracts the liquid and the materials it contains toward the aspiration orifice of the system It indicates the negative pressure that is created in the aspiration line of a system fitted with peristaltic pump when the aspiration orifice is occluded by material which reduced the flow in the aspiration tube to the point of interrupting it. Vacuum can be reduced or drop to zero depending on whether the aspiration line is freed partially or totally.

Rise time::

Rise time : It is time taken by machine to reach the vacuum to its preset level once occlusion occurs. Rise time is inversely proportional to the AFR. Shorter rise time translate to a rapid occurrence of events in anterior chamber. This rise time depends upon the value of the flow rate as well as characteristics of the pump RT is linear and fast in venturi pump,depends on preset vacuum.In peristaltic,depends on flow rate.

surge::

surge : Phenomenon that can cause collapse of the anterior chamber when there is an occlusion break during nucleus removal. The increased vacuum at this time in the aspiration line tends to draw fluid rapidly out of the eye called as surge. Methods of preventing surge : 1. Venting: Venting is system which allows vacuum level to be equilibrated to air or fluid into the aspiration line. 2 methods: Fluid venting and Air venting Fluid Venting usually opens a solenoid for irrigation fluid to enter the aspiration line Air venting systems open the aspiration line momentarily to the atmosphere. 2. Decreasing the effective flow rate : Without changing the actual setting on the machine, the surgeon can decrease the effective FR by using a smaller bore aspiration port, e.g. Microflow tip

Surge(cont..):

Surge(cont..) 3. Modification of phaco tip : ex.ABS tip 4. Increasing the infusion : by raising the bottle height 5. ACM: use of it is useful for decreasing surge (especially for beginners). 6. Proper wound construction : A leaking wound will disturb the equilibrium of the chamber so that even a very small amount of fluid withdrawn can cause it to collapse. 7. Increased viscosity of the AC contents : The flow rate settings are for clear fluids like BSS/Ringers. A thicker fluid increases the resistance and does not flow out easily. The use of VES can cause a decrease in the effective FR and thus decrease the surge. 8. Foot control : Above all, good foot pedal control is of paramount importance in controlling surge and utilizing it to your own advantage.

Reflux::

Reflux: This is how positive pressure is created inside the aspirating tube to invert the direction of the flow and discharge the material that is already in the aspiration line. Regurgitation occurs when the vent pulse pressure is greater than the irrigation pressure and is visualized by return of the aspirated material into the anterior chamber. This function is important clinically in order to avoid tearing the tissue that has occluded the aspiration orifice in the event of iris or capsule capture

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