Surge occurs during phacoemulsification when outflow exceeds inflow, and a sudden rush of fluid from the anterior chamber occurs post-occlusion. Tip excursion or stroke length is defined as the distance the tip displaces in the longitudinal direction at maximum power. This unit is where all the fun begins.

Whenever the phaco power is set at percent, the stroke length is the maximum permissible for that machine. The irrigation is on, and the vacuum and aspiration level is at its highest preset level. Low vacuum is helpful during sculpting of a hard or large nucleus, in which the high power intensity of the tip may be applied near the iris or anterior capsule.

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The illustrations are superb, demonstrating clearly how phacoemulsification works and why some maneuvers must, necessarily, work better than others. The part of the phaco machine which moves fluid through the aspiration tubing. And on the top we've reach our maximum pre-set vacuum by the red bar with. Excellent explanation of concepts complemented with simple and clear illustrations.

Phacodynamics - EyeWiki

Over the years, your books have a had a tremendous impact on ophthalmology and all of cataract surgery. Residents and Fellows contest rules International Ophthalmologists contest rules. JoshuaHirth Great Presentation! Another source of fluid loss is through wound leakage.

Or F, change from a peristaltic pump to a vacuum pump. If you continue browsing the site, you agree to the use of cookies on this website. And these have different ways of functioning at the time of cataract.

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And the easiest of these is actually just to lower your flow rate and. Understanding the mechanical principles underlying this technology allows the surgeon to optimize machine settings and safely trouble shoot problems encountered during surgery. So essentially if you think of the extreme of foot pedal depression in this case. And as the gas is pumped through the housing, there is a force that is directly. Linear control instead of fixed control allows more control over the amount of energy being applied.

But again in this case the pressing the foot pedal does not increase the power. This causes forward movement of the iris, lens and posterior capsule. And then lastly, there is the breakdown of the blood-aqueous barrier which has also.

It is a good start and has a lot of fluid dynamics that we do not think about all the time. Also referrerd to as variable control. There are also hybrid systems that incorporate both types. And this white box actually represents the pump which we'll talk about more.

All phaco machines permit the user to alter phaco power and this is usually indicated as a percentage. This length is generally mils thousandths of an inch. So the phaco power is set beforehand by the surgeon. So to first understand phacodymanics, we have to understand phacoemulsification. So let's talk about phaco pulse, which is one of these ways where phaco.

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And so what happens is vacuum actually has to build up to our preset maximum. This can be done by making sure the fluid entering the eye is equal to the amount that exits. Peristaltic pumps control the outflow of fluid through the movement of a series of rollers over flexible tubing. Adjustments to duty cycle, which is the combination of phaco and rest time, and power modulation with pulsed, burst and hyperpulsed phaco power can optimize efficiency during surgery.

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These three lines correspond to the three phaco foot pedal positions. Occludability is the tendency of the tip to get occluded, giving rise to a buildup of vacuum. And the technology of phacoemulsification has advanced rapidly. Enroll in the International Ophthalmologists contest. The phaco needle, moving at ultrasonic speeds, creates intense zones of high and low pressure.

And today, we will be speaking about phacodynamics. Phacodynamics From EyeWiki. But it requires a knowledge of phacodynamics. Total power is a combination of the frequency of the needle movement and stroke length. The compression than the subsequent expansion.

So the surgeon sets both the flow rate as well as the vacuum. Both safety and efficiency of phacoemulsification cataract surgery are directly related to fluidics. When the power is decreased by a given percentage, the stroke length also decreases.

And the speed of the rollers determine the flow rate. Now customize the name of a clipboard to store your clips. Professor and Retina specialist Follow. Surgery can then be customized moment by moment for each individual patient to maximize safety and efficacy.