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Cataract surgery by Phacoemulsification is the standard of care today and there are a lot Author, Manual of Phaco Technique (Text and Atlas). ○ Advisor and. Phacodynamics. Mastering the Tools and Techniques of Phacoemulsification Surgery, PDF CD-ROM. Fourth edition. by Barry S. Seibel. Book Review Phacodynamics: Mastering the Tools and Techniques of Phacoemulsification Surgery; Download PDF. 26KB Sizes 10 Downloads 55 Views.


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Phacodynamics and Phacoemulsification - Free download as PDF File .pdf), Text File .txt) or read online for free. Download ebook: Phacodynamics: Mastering the Tools and Techniques of Phacoemulsification Surgery. Phacodynamics by Barry S. Seibel, , available at Book Depository with free delivery worldwide.

A clear understanding of the physical and mechanical principles that govern phacoemulsification can facilitate usage of this technique for effective and efficient cataract removal It is essential to understand the basic principle of phacodynamics. This is even more relevant to bimanual microphaco and is mandatory for the evolution of this technique.

Phacodynamics is defined as the study of the funda- mental principles of inflow rates, outflow rates, vacuum, phaco power modulation along with microsurgical maneuvers with different types and grade of cataract. A true understanding of this will help in logical setting of the machine parameters in adaptation to different surgical techniques.

Even the most modern machine will not give adequate results as compared to an older machine if the principles of phacodinamics are not well understood. Most of the surgeons use their equipment without really understanding their machines or the basic values which allow them to operate in great safety. The most important parameters in microphaco- emulsification, in order to be performed well requires a good understanding of fluid mechanics.

Basically the dynamics of phaco in both conventional and microphaco remain the same I n microphaco irrigation is through the side port rather than through the irrigation slevees Fig. With this one of the major problems encountered is that not enough fluid is going into the eye through the side port irrigating chopper. Some of the obvious advantages of bimanual micro- phaco are decreased incision size, less astigmatism, good anterior chamber maintenance if we understand the logic of phacodynamic.

Because irrigation is separated from aspiration the added advantage theoretically is that all fluids comes in through one incision and exit through the other. We have always to take in account some leak from the irrigation sideport and from the aspiration sideport thats we demonstrate in our experimental set-up.

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The disadvantage is it requires expensive equipment, you have problems with maintenance, and you have disposables in most machines where you have ongoing costs with every case. But it has uses even in poor and developing countries. That is changing in several countries. But it can be used to generate income, even in very poor countries. An example of where this is used is the system in southern Indian. It was started by Dr.

There are at least 45 million people who are blind from cataracts. He started in with an 11 bed hospital. The system has grown. There are now several hospitals that are high volume and high quality. Most of the surgeries are done with small incision ECCE.

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About one thirds of the patients pay, and those patients generate enough income that about two thirds of the patients are done at no charge. You have an Ultrasonic tip that vibrates like a miniature jackhammer.

It moves forward and back. It does it very fast. You have to have a cycle rate of 35 to 40, cycles per second to overcome inertia, and it only cuts on the forward stroke. Aspiration has to pull the material back to the tip, and you get another forward stroke very rapidly, and it cuts into small pieces or emulsifies. The basics of the machine are pretty simple. You have fluid in flow, you have a bottle, usually, with balanced salt. And most machines use gravity flow, so the bottle height and port size control the rate of flow in the machine when the valve is open and can let fluid in.

You have an aspiration pump, which pulls material to the tip in the eye, and then pulls the emulsified material on through the eye into a disposal bag. Vacuum is generated when the material, the tip is occluded. The handpiece has an electrical input to cause the vibration. You have irrigation line, which brings fluid in from the bottle. Then when the pump is running, fluid is aspirated through the end of the tip and through the aspiration line.

This is a schematic, basically, of how machines work. You have a bottle of fluid. The tubing goes through a pinch valve, and when the pinch valve is open, fluid is irrigated through the tip, through the side ports, and into the eye.

When you have a pump, then, which pulls fluid through the end of the tip, and through the pump and into the disposal bag. You set the maximum vacuum you want.

A major advance was the torsion al phaco.

You have side to side sweeping motion instead of forward and back like a jackhammer. It goes side to side. It shaves and cuts it on both directions of movement. It shows longitudinal and torsional. Know that PEA is fast. The efficiency of the torsional tip comes from its action. The boring and slicing action of phaco cutting to the shaving action of torsional emulsify. It is fast and effective. You control the machine with a foot pedal. This is the diagram of the foot pedal.

Phacodynamics: Mastering the Tools and Techniques of Phacoemulsification Surgery, PDF CD-ROM

Push down a bit more and you will hear the phaco power coming in. Zero, your foot off of the pedal and nothing is going in or out of the eye. Position one, you will hear a click and that opens the valve. It lets fluid flow into the eye, intraocular pressure is going to be equal to bottle height. You need a snug fit, but not too tight.

You need a precise incision size to get there. Foot pedal position two, press down further. It adds aspiration, pulls fluid through the eye into the phaco tip and out of the eye. The flow rate depends on how fast the pump is running, and you set flow rate in mm per minute.

Foot pedal position three, your valve to the bottle is open, so you have inflow. You have aspiration. The pump is running. And position three, going down a little further in the foot pedal, you hear a buzz when you hear phaco power starting. You pretty much always want to use linear control. The more you push down, the more power you get up to your preset maximum. So, I always set it to linear. You want to use enough pow tore cut the material.

I primarily use torsional power with very hard nuclei. Vacuum level depends on how tightly the tissue is held when the tip is occluded. And vacuum increases proportion ally to. This rise time.

This is an illustration. If you double your speed, you should get rise time to vacuum in half the time, in two seconds.

You have different vacuum settings and aspiration rates for different parts of the procedure. Typically for irrigation aspiration, you have a smaller opening. Something you have to be aware of is surge. And you can get collapse of the chamber and tear a capsule pretty easily. So, the last bit, you want to be slow and ginger about using a little bit of phaco power at a time. Some newer machines have what is called active fluidics. Instead of just depending on bottle height for flow, it actively senses and adjusting to ocular pressure.

This helps to stabilize the anterior chamber and capsule. This demonstrates the green line is what typically happens with a gravity feed system. As operation rate sets how fast fluid is pulled through the eye.

You can include to 20 to 50 for quadrants. You want to hold them against the tip more firmly. You want to adjust the rate, and you watch how the material is moving. Bottle height with gravity systems determines the flow into the eye, and you have stability of the anterior chamber and posterior capsule. You have to have an even balance between inflow and outflow. The systems with active fluidics, you set the targeted intraocular pressure, setting it at 55mm is approximately equivalent to 95cm of bottle height, which is usually as high as the average gravity feed system goes.

Again, you want to have an aspiration rate fast enough to keep tissue moving to the tip, but not so fast that you have instability to the chamber.

If it is jerky, slow it down in that case. Phaco power. You can hear the sound of the vacuum rise in pitch. Then use a little phaco pow tore emulsify the tissue.

Normally you are most efficient if you use phaco in short bursts of one or two seconds and then go back to just aspiration. If you do, a piece will fall off, and you have to go back down and get it again, which is time consuming and also dangerous.

Phacodynamics : Mastering the Tools and Techniques of Phacoemulsification Surgery

You have material moving around in the capsule or mag. Once you have contact with the tissue, the vacuum is building, then you can add enough phaco power to emulsify the pieces. Short bursts of a second or two are more efficient than always, you go into phaco, back into aspiration, and back into phaco. Pre phaco is basically just aspirating the soft material on top of the nucleus.

And how much there is depends on how hard the nucleus is, typically. Very hard nuclei have little to no. Normally you need aspiration, little flow and little vacuum for aspirating on top of the hard nucleus. You want to leave an edge of epinucleus and cortex. This gives you an edge for later. Use just enough linear power to cut and go through. You only want to cut moving forward. When you start back to get another shot at it, go back to position two. Sometimes you can have a very hard nucleus, and you have trouble grooving it.

You can increase your power.

And it will cut most nuclei. Most procedures, you start dividing the lens in pieces. You want to go down until you have an even red reflex all the way across. Then you use your tip and your second instrument to split it. That first split is very important.

Divide and conquer. You get your first division, rotate the lens, groove and divide it, so you have an X groove and you have four pieces of the nucleus.

You stay well away from the posterior capsule. This shows the typical divide and conquer procedure. You have to go down until you get an even red.

Then use the two instruments in the groove to split. Rotate 90 degrees. Make your second groove. You can see the gray material will? Remember the lens is a lot thicker in the middle, so you have to go deeper there than you do peripherally. Make your third groove. Split it. You want to split all the way to the middle, so you free up the pieces from each other. Then you increase your power, vacuum, and aspiration, and emulsify each quadrant.

Cortex removal is done normally with an irrigation aspiration handpiece. The vacuum to , rate of ml per minute. And it works best if you do the sub incisional cortex first while the rest of the cortex is helping hold the bag open.

You start sub incisionally and work around. You can manipulate each irrigation and aspiration separately. A silicone or plastic tip is safer than a metal tip, if you can get one.

So phaco steps are prephaco, making a groove for most procedures. Removing the hard nucleus. Then the epinucleus, it is thicker than cortex but considerably softer than the hard nucleus in most patients. Then in irrigation and aspiration, you remove the cortex, polish the capsule and remove after you put the lens in.

Phaco may stop cutting. The anterior chamber depth may be unstable. Tip may clog. You may not get any aspiration. You may get a capsule tear. You definitely will get capsule tears, and you can get wound burns. If the phaco stops cutting, worry is there a capsule tear?The anterior chamber is unstable? You will have to decide what to do to finish the case.

Phacodynamics: Mastering the Tools and Techniques of Phacoemulsification Surgery

Short bursts of a second or two are more efficient than always, you go into phaco, back into aspiration, and back into phaco. Practice as much as you can in a wet lab. This tends to make mobile anterior chamber structures such as the iris to tend to move towards the port of the phaco tip. The system has grown.

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