SYMPOSIUM ON BASICS OF PHACOEMULSIFICATION
MODERATOR - Dr. BALMUKUND AGARWAL
INSTUMENTATION AND MACHINES IN PHACOEMULSIFICATION
PRESENTER - Dr. KRATI GUPTA
MODERATOR - Dr. BALMUKUND AGARWAL
INTRODUCTION
Phacoemulsification surgery was invented by Charles Kelman in 1962.
Phacoemulsification machines have undergone constant improvement, ever increasing both their complexity and safety.
Phaco surgery is machine-dependent surgery so to understandthe basic functioning of the phaco machine is integral for success of phacosurgery.
Simplicity of phaco surgery depends upon how well one knows the machines.
INTRODUCTION
Complication rate is reduced with good knowledge of surgeon’s own phacomachine.
One should give sufficient time to accustom and to customize the parameters related to steps of phaco surgery
All phaco machines consist of a computer to generate electrical signals and a transducer to turn these electronic signals into mechanical energy.
INTRODUCTION
The energy thus produced is passed through a hollow needle and is controlled within the eye to overcome the inertia of the lens and emulsify it.
Once turned into emulsate, fluidic systems remove the emulsate, replacing it with balanced salt solution (BSS).
SCHEMATIC REPRESENTATION OF THE PHACO MACHINE
The phacomachine broadly consists of :
1. Console
2. Foot pedal
3. Handpiece and their connections
PHACOMACHINE
The console consists of a computer which controls all the functions of the machine.
It contains basic hardware and software of the machine.
The computer generates ultrasonic waveform and sends it to the transducer in the form of electronic signals.
CONSOLE
The setting for the various parameters, i.e. power, vacuum and flow rate are fed in here.
These settings represent the maximum level of the parameter that will be achievable: the further linear control is with the foot pedal.
CONSOLE
Newer machines have a multi-mode panel, where multiple settings of all variables, as is required by different surgeons,can be fed in.
The same surgeon may like to change all the variables during the surgery and these parameters can also be fed in and can be recovered by touching the memory button only.
Settings for different types of cataract can also be fed into the memory.
In some machines the memory can be activated by the foot switch so that the surgeon can continue the surgery without having to look at the console.
CONSOLE
PUMPS
Three types of pumps are present:
1. Diaphragmatic pump
2. Venturi pump
3. Peristaltic pump
DIAPHRAGMATIC PUMP
A diaphragm pump is having flexible membrane to generate vacuum.
With this pump vacuum reaches to preset level without occlusion.
This mechanism is easy to remove small pieces but safety margin is less.
VENTURI PUMP
There is no discrimination between vacuum and aspiration flow ratemeans that both are working together.
Principle:
Compressed gas creates a negative suction force that is the vacuum inside a closed chamber which is directly transmitted to the handpiece.
VENTURI PUMP
ADVANTAGES DISADVANTAGES
Surgical procedure is fast Being a fast machine the safety zone is less
Vacuum works more efficiently and thus holding capacity of the
machine for the tissue is better.
Catching of iris and iris chaffing
Catching of anterior and posterior capsule is common.
PERISTALTIC PUMP It is one of the most widely used pump in the practice of phaco.
Vacuum and aspiration flow rate work independently, but finally assisting each other.
Principle:
In peristaltic pump the rotation of the rollers by the pump pinches the soft silicon tubing, which creates a negative pressure by squeezing the fluid out of the tube.
In this system the vacuum will be built up only when the tip is occluded.
PERISTALTIC PUMP
ADVANTAGES DISADVANTAGES
Safe machine According to some surgeon’s point of view it is a slow machine.
Complicated cases can be handled safely and in a skillful way
Chances of catching of iris, capsule is less.
TUBING
Phaco machine attaches to the phaco probe via this tubing.
Two functions of the tubing are irrigation and aspiration.
These tubings are made up of silicon material which can be autoclaved or ethylene oxide (ETO) sterilized.
With the higher end machines one can get pre sterile pouch of tubing which is called as cassettes.
Phaco fluidics depends upon the quality of tubing.
TUBING
Factors determining the quality of reusable tubing are:
Color: Yellow color indicate an old tubing which should ideally be changed.
Consistency of the tubing: Hard consistency of tubing which is not flexible should be changed.
TUBING
Fitting: Ends of the tubing which are attached to the machine andthe phaco probe should not be loose.
If the ends of the tubing are not smooth or appear damaged thenthe tubing should be changed.
Cassette – in higher end machines disposable cassette are used.
PHACO PROBE
It is a piezoelectric substance which converts electronic energy tomechanical 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.
PHACO PROBE
PARTS
1. Phaco Handpiece
2. Irrigation aspiration handpiece
3. Phaco tip
4. Wrench
PHACO HANDPIECE
The phaco handpiece contains the piezoelectric crystal, which is in contact with the tip.
The tip is covered by a silicon sleeve.
The infusion fluid flows between the tip and the sleeve cooling the former.
PHACO HANDPIECE
There are two openings on the sleeve for the exit of this fluid, which should be kept perpendicular to the tip bevel.
The proximal end of hand piece 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.
PHACO HANDPIECE
Functioning of the probe is to deliver the energy which cuts the hardpart of cataract which is the nucleus.
The mechanism of working is by:
1. Jackhammer effect: It is the direct mechanical impact on the nucleusto cut it.
2. Cavitational impact: With the gap between the phaco tip and thenucleus the bubbles form in irrigating fluid in this gap which cutsthe tissue
PHACO HANDPIECE
3. Acoustic wave of fluid: This is generated by the forward movementof the tip, can disintegrate the lens material.
Power of the machine depends upon the stroke length and thefrequency remains fixed.
OZIL TORSIONAL HANDPIECE
Greater Phaco Efficiency
The OZil® Torsional Handpiece features side-to-side oscillating ultrasonicmovement. The result is a wide range of benefits duringphacoemulsification procedures.
1. Reduces Repulsion
Ultrasonic oscillations cut lens material using a shearing effect
Eliminates repulsion associated with traditional ultrasound induced by thejackhammer effect
Side-to-side movement increases cutting efficiency by emulsifying lensmaterial with both directions of movement
OZIL TORSIONAL HANDPIECE
2. Improves Followability
Lack of repulsion facilitates occlusion and effective delivery of energyinto nuclear fragments.
Improves followability and decreases dispersion of nuclear fragmentsduring emulsification.
Reduces irrigation fluid consumption and increases your surgicalefficiency
3. Improves Thermal Safety Profile
Operates at cooler temperatures than traditional ultrasound.
PHACO TIPS
The phaco tip is made of titanium and is hollow with the distal opening functioning as the aspiration port.
The acoustic energy produced along the ultrasonic handpiece is then transmitted onto the phaco tip.
The angulation of the tips may vary from 0–60°.
Tips with 60°, 45°, 30°, 15° and 0°angulation are available.
PHACO TIPS
More the angulation, the lesser the holding power but the cutting power is more, e.g. 60°tip is a sharper tapered tip making occlusion difficult.
Therefore, this tip has a better cutting and less holding power.
PHACO TIPS
The 45° tip has a very good cutting ability and was very popular initially as the emphasis was then on ‘Divide and Conquer’ in which trenching (thus cutting ability) was more important thanocclusion.
With the advent of aspiration phaco the most popular tip today is 30°. This has adequate holding and cutting power and is useful both for trenching and in chopping.
The 15° and 0° angulated tips are better for holding but have a poorer cutting action.
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.
SLEEVE
There are two openings 180° apart on the sleeve through whichirrigating 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.
SLEEVE
The distance between the distal end of the phaco tip and that of thesleeve (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 thesleeve over the phaco tip and this finally plays a very important role inphaco fluidics.
Sleeve is autoclaved or ETO sterilized.
TEST CHAMBER
It is again silicon-made and is helpful for tuning of the machineand before start of the case it is useful to have an idea about theparameters of the machine in the test chamber.
If a small nucleus particle is stuck in the tip or aspiration tubing, itcan be removed in the chamber with BSS solution in the energymode of the machine
PHACO WRENCH
Phaco tip is screwed into the handpiece by wrench
IRRIGATION-ASPIRATION (I-A) HANDPIECE
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.
IRRIGATION-ASPIRATION (I-A) HANDPIECE
The opening can be in a diameter of 0.2, 0.3, 0.4, or 0.5 mm.
The angulations of the I-A handpiece can be straight, 45°bent, or has a 90° bend.
FOOT PEDAL
Foot pedal control is the most important aspect of phaco.
Though the foot pedal of each machine may have a different design, it essentially consists of main central part and side kicks.
The main part of the foot pedal controls infusion, aspiration and phaco power.
The entire distance that the 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).
FOOT PEDAL
The excursion before the first dentation is the I excursion.
The excursion between the 1st and the 2nd dentation is the IA excursion.
The excursion after the 2nd dentation is the IAP excursion.
Resistance is felt at the dentations or position where the mode changes and it is to feel these dentations that one has to train oneself both while depressing and while coming back up.
FOOT PEDAL
FOOT PEDAL
Familiarity with the feel of dentations of the pedal (tactile feedback) and the sounds that the machine makes (auditory feedback) is mandatory before attempting phacoemulsification.
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.
FOOT PEDAL
In the I excursion, the pinch valve opens and irrigation is switched on.
There is no gradient in this step and the irrigation is either switched fully on or off.
In the absence of gradient, the function of this dentation is to dissociate infusion from irrigation-aspiration.
As foot is brought back from IA/IAP excursion, stopping at this dentation will keep the infusion on preventing the collapse of anterior chamber.
FOOT PEDAL
Many steps like nuclear rotation, manipulation of nuclear fragments, epinuclear plate etc. require a formed AC without any aspiration.
Dentation 1 to dentation 2 is the aspiration or the IA excursion.
From dentation 2 to full depression is the phaco or the ‘IAP’ excursion.
FOOT PEDAL
At IAP0 phaco energy delivered will be zero and at IAPmax the energy will be maximum preset.
The delivery of phaco energy is linear both in the surgeon and the pulse mode.
However, in panel or burst mode, as soon as foot clears IAP0, maximum preset energy is delivered.
FOOT PEDAL
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. 100mmand the maximum preset phaco energy is 100%, then the foot gradient (FG) becomes:
Decreasing the maximum preset power on console increases the foot gradient and hence the foot control.
Therefore, 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
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.
