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Vertical chop is my preferred approach for medium and hard cataracts, with some variations for very hard lenses. Executing vertical chop requires expert understanding, management of fluidics, and an effective phacoemulsification platform. The vertical chop technique takes advantage of the natural cleavage planes that exist within the nucleus to fracture it in several fragments using minimal energy.
Compared with sculpting, vertical chop has several advantages, including 1 reduced use of phaco power and phaco time, which means less ultrasound energy use; 2 reduced stress on the zonules because the nucleus is held by the phaco tip, receiving all the stress induced by surgical maneuvers this is particularly important in eyes with zonular weakness ; 3 no need to depend on the red reflex to assess the deepness of the groove; and 4 the ability to perform nucleus fracture with all surgical maneuvers within the central 3 to 4 mm, which is especially helpful in the case of poorly dilated pupils.
Overall, vertical chop is more efficient for standard cases compared with divide-and-conquer or horizontal chop techniques, but it is especially effective for complicated surgeries such as those with small pupils, loose zonules, brunescent nuclei, or mature white lenses. We use topical anesthesia and intracameral lidocaine. After an injection of 0. Should multifocal IOL implantation be planned, the incision is placed at the steepest meridian. A circular, well-centered 5. We find this to be the most efficient combination available.
When using the IP feature, no settings changes are necessary. We enable the Ozil IP feature only for quadrant removal and is activated only when a specified percentage of the vacuum threshold is reached. We also advise positioning the tip using an outside-in approach, as this is helpful in maintaining the ongoing emulsification of the lens material.
Nucleus fracture. We perform vertical chop using a Rosen chopper Katena Products, Inc. Proper placement of the phaco tip is crucial. It must be embedded deeply into the center of the nucleus, pointing toward the optic nerve, with high vaccum and burst mode Figure 1.
We find burst mode particularly advantageous for chopping. Once the tip has reached the desired depth and is occluded, the footpedal is held in position 2 to stabilize the nucleus. The tip of the chopper is then stabbed into the nucleus 1 mm in front of the phaco tip. The chopper moves downward while the phaco tip moves upward Figure 2A. When the chopper and phaco tip are close together, a lateral movement splits the nucleus into halves Figure 2B. Whenever subincisional cortex removal becomes difficult, it may be a good option to use two separate cannulas, one for irrigating the anterior chamber and the other for aspirating cortical material.
We do not enlarge the incision. Vancomycin for infection prophylaxis is injected intracamerally at the end of the procedure. Vertical phaco chop can be performed in small pupils Figure 3 in which it may not be advisable or safe to take the sharp chopper peripherally toward the equator or where the groove of a divide-and-conquer technique cannot be extended safely to the periphery.
Also, because the nucleus is held by the phaco tip and forces act in a vertical plane toward the tip, no stress is placed on the zonules. Minimizing stress to the zonular apparatus is of benefit in every cataract surgery, but particularly in cases with zonular weakness.
It requires higher-power ultrasound and prolonged phaco time. The main modifications of each surgical step for success with hard cataracts are as follows. Local anesthesia is recommended in cases with weak zonules, poor patient cooperation, or risk factors for intraoperative complications.
When the red reflex is poor, we must stain the capsule with trypan blue 0. OVD plays an important role in protecting the endothelium in hard cataracts. Phacoemulsification of hard lenses presents two main risks: greater endothelial cell loss and increased risk of posterior capsular rupture. Furthermore, dividing the hard nucleus is difficult; posterior layer fibers can be cohesive and tenacious and resist all conventional methods of division. Extra precautions must be taken to protect the endothelium and the posterior capsule.
But this also makes it more difficult to get occlusion. Mini-flared tips, supplied by Alcon Laboratories, Inc. Fort Worth, Texas , are for use with torsional ultrasound. What determines the settings for a given phaco tip? First, the amount of irrigation fluid entry into the eye is a key factor. Other factors include the amount of leakage from the eye, most often through the sideport. The internal diameter of the phaco needle at its thinnest point is crucial to fluidics settings because of the physical principle of Poisseiulle's Law, which determines the resistance to flow through a cylinder.
Small increases in the cross-sectional diameter will increase the area of the cylinder by greater amounts. Therefore, the amount of resistance decreases as the diameter increases; as the diameter decreases, the resistance increases. Why is tip design important? Different tip designs enhance the way the nucleus is broken down, with the size of the tip influencing the way tissue is removed. Add-itionally, the shape of the needle affects the efficiency of cutting. For example, the movement of the curved Kelman tip makes it a better cutter than a straight needle, particularly with dense cataracts.
Optimal tip design also depends on the type of energy being used—longitudinal, torsional OZil; Alcon Laboratories, Inc. With transversal energy, for example, a straight tip creates enough movement to remove tissue as it moves. Torsional energy requires a curved needle. The backward and forward movement of a straight needle also removes tissue, but not as efficiently due to repulsion of nuclear material.
Another factor when deciding on tip selection is your technique. If you are chopping, you want to try to hold the nucleus as firmly as possible without pulling nuclear tissue through the tip. You should be in foot position 2. As already mentioned, with torsional, clogging may be eliminated by using a tip with a sharper bevel; however, this may make chopping more difficult because of the more open bevel.
For example, the tip used with the Infiniti Alcon Laboratories, Inc. This tip penetrates the nucleus from above, with good occlusion during chopping.
There are phaco tips designed for sub—2-mm incisions. They both have restricted central diameters that can slow down surgery and require high vacuum to work efficiently. There are also differences in sharpness of the phaco tip. In the past, only sharp needles were used because they penetrated all cataract types easily. Rounded tips seem to break up cataracts just as well as sharp tips.
This tip can remove hard nuclei even though the end is not sharp. This tip works well with the prechop technique. It is a fluidics-driven phaco tip. Akahoshi has also designed a square tip for use with torsional ultrasound. Surgeons often disclose that they use a vacuum of mm Hg; however, few disclose what needle they use.
More than likely, it is because they prefer a narrow phaco needle. In the absence of high vacuum, it would be impossible to clear the nuclear material from the eye with a narrow tip.
Alternately, the vacuum need not exceed mm Hg with a gauge needle. Phacoemulsification should be fluidics-driven rahter than energy-driven. Energy is required to assist the fluidics to draw the nuclear material through the phaco needle. The bottle should be adjusted to the height that will allow adequate inflow.
The idea behind this movement was to cut lens material, avoid repelling lens fragments and to emulsify lens material on both ends of the motion.
Now with IP, you never come to a complete occlusion, because the IP system will kick in just enough longitudinal movement to break any occlusion or pre-occlusion state. As a result, you get a much more stable anterior chamber. And on the harder cataracts—where we had to be concerned with clogging and thermal issues—such concerns are greatly lessened. If you do a grooving technique and you get IP activation, that avoids getting an occlusion and causing problems, and you may realize you need more phaco energy to avoid reaching that higher vacuum level again, and so you can keep your tip clear.
Jones continues. The extra energy will help keep your tip clear and avoid getting an occlusion. At the beginning of the surgery, we all have a sense, based on our grading of a cataract, whether it will be dense or mild. But, sometimes, there will be a cataract that surprises us by how dense it is. You can get a sense of this density by the IP activation. If you have a lot of IP activation, it prevents you from getting an occlusion because it will push the piece away and let you reacquire it at a different tissue interaction face.
When it goes up a grade, for example, the machine can be programmed to increase aspiration flow rate, vacuum and bottle height. It can also modify the power modulations on the OZil handpiece. In this way, you waste less flow of fluid through the eye, and waste less time and energy at those lower levels of fluidics and power.
Though Dr. AMO Whitestar Signature. AMO initially enhanced the cutting efficiency of its Whitestar Signature system by offering Ellips ultrasound, which blends longitudinal ultrasound with transversal ultrasound in an effort to avoid clogs while still emulsifying lens material.
In the past year, however, the company added a wrinkle to its Ellips ultrasound called Ellips FX. This makes it more efficient in terms of removing different types of nuclei. The second innovation is non-zero start. This also seems to improve followability significantly. Fishkind says these changes have affected how he approaches cases. So with non-zero start and highly controllable fluidics, removal of harder nuclei is more efficient since the device can hold the nucleus at the tip without allowing occlusive surge and instead fosters a steady, slow emulsification of the material.
You can also chop nicely because you can use burst power to get into the nuclear material and hold it to do vertical chop. I do vertical chop currently, which I think is a more gentle, controlled way to remove the nucleus. The Whitestar Signature system facilitates such chopping techniques.
The Vizual, which has a peristaltic pump, uses a kHz handpiece that has the option of using burst and micropulse phaco.
This is engineered toward maintaining a cool incision site. To keep the surgeon from having to alter power and fluidics settings throughout the procedure, the Vizual also offers multi-modulation, or the ability to define three phaco modes that each have different phaco settings, such as burst or micropulse.
Cameron explains. The system also allows 24 different users to save their mode settings. To help avoid surge, the system uses an anti-surge system built into the software that controls the ramp up and ramp down of the peristaltic pump. He says that, even if he has to enlarge the 1. From there, I think it is a matter of slowly adjusting things and refining those adjustments as you see how your modifications affect fluidics in the [anterior chamber.
Small, intentional adjustments of a single variable can make a significant difference in efficiency and safety. With Dr. Chen as the moderator, the panel was composed of David F. The webinar delved into how surgeons can best set their phaco machine parameters and how to modify those settings for more complicated situations or when complications arise. The expert panel first reviewed the basics of why and how to choose settings for aspiration flow, vacuum, and power modulation.
Chang first explained that aspiration flow rate determines the speed at which things happen. Therefore, when facing a tough case, trying a new machine, or transitioning to a new phaco technique such as chopping, surgeons should slow the procedure down by lowering the aspiration flow rate. Vacuum, he said, determines the grip and holding power. Chang said. Chamber shallowing occurs when too much fluid surges into the phaco tip as soon as occlusion breaks from a high vacuum level.
We know that the cornea can collapse from excessive surge, but consider that the posterior capsule can flex forward with relatively minor levels of surge. Chang said that the most important advances during the past decade have been with phaco power modulation. This maintains cutting efficiency, while reducing the repelling action of pure longitudinal phaco that tends to kick microscopic nuclear fragments toward the corneal endothelium.
Cohen said the most important factor for distal followability is aspiration flow rate, or you can be in foot position 2 and bring the phaco needle closer to the fragment to have the same effect without increasing flow rate.
Once the fragment is in the center, it is held in place for phaco by vacuum. Chang said one can use linear control of vacuum in foot position 2, with a very high maximum setting due to the small aspiration port. I first access low vacuum e. Then I need a — mm Hg level to grab and grip the cortex without evacuating it.
This level allows me to strip and peel the cortex away from the capsule. Once the cortex is free and safely held mid-pupil, I maximize vacuum by flooring the pedal and fully evacuate it. Subincisional cortex is addressed first because it holds the capsular bag open, Dr. Cohen said, and allows the posterior capsule to remain protected by a layer of cortex should you happen to grab posteriorly.
Chang said his main pearl for subincisional cortex removal is proper hydrodissection. In a more challenging case, such as a deep anterior chamber, Dr. Cohen said you have to worry about reverse pupillary block, and may have to lower the bottle for a more stable anterior chamber, using a small instrument to lift the iris off of the anterior capsule and releasing any trapped fluid. With high myopes, although one can undo pupillary block once it occurs, it is better to prevent it from occurring, Dr.
Irrigation fluid simultaneously flows into the anterior and posterior chambers, thereby preventing lens-iris diaphragm retropulsion syndrome from occurring. The faculty then addressed a complication: posterior capsule rupture. Chang emphasized the need to remain calm. Surgeons should mentally rehearse what needs to be done in this scenario.
Surge occurs when a fragment that is occluding the port is suddenly aspirated. When the fragment is occluding the phaco tip, the tubing collapses due to negative pressure. When the fragment clears, there is a sudden expansion of the tubing causing a rapid rush of fluid into the tubing and subsequent flattening of the anterior chamber.
Surge is often associated with the rigidity of the tubing. The more pliant the tubing, the higher the likelihood of creating surge. To help control surge, the surgeon can increase the inflow into the eye with a higher bottle height, lower aspiration flow rate, and lower vacuum preset.
These include digitally controlled and automated infusion systems, rigid tubing, and a bypass port to allow some flow even when the tip is occluded. Altering the fluidics for the density of the cataract can be advantageous. With weak zonules, the entire diaphragm of the capsular bag tends to trampoline up and down, so the goal is to stabilize the chamber. By doing so, this can prevent the vitreous from prolapsing anteriorly and hopefully prevent the need for a vitrectomy. As inflow decreases with a lower bottle height, I decrease the vacuum and decrease power to about Although wound burn is less common with todays advanced phaco technology, it still is something every surgeon tries to avoid.
A few surgical pearls to prevent a wound burn are to aspirate some of the viscoelastic material before beginning to sculpt or vacuum the lens and to ensure proper incision architecture.
Make sure the incision size is appropriate, the entry into the anterior chamber is square, and avoid torquing the wound when using the phaco handpiece.
Paying close attention to these types of small details are the basics of phaco fundamentals. Henderson is in private practice at Ophthalmic Consultants of Boston, and clinical professor of ophthalmology at Tufts University School of Medicine. She can be contacted at bahenderson eyeboston. The evolution of modern cataract surgery is exciting because of rapid technological advances that now allow surgeons to modify phaco settings in order to increase patient safety and decrease healing time.
The trend has been to minimize phaco energy in order to protect corneal endothelial cell loss, and an understanding of power modulation is an important step toward achieving this goal. There are two basic principles to consider regarding power modulation: the direction of phacoemulsification—longitudinal, transversal or torsional—and timing—continuous, pulse, burst, as well as hyperpulse and hyperburst.
Traditional longitudinal phaco uses a jackhammer-like motion, in which the tip moves forward and backward.
However, it has been recognized that when the tip moves backward, energy is being produced but not breaking up the lens, resulting in unnecessary heat production. With transversal ultrasound, longitudinal phaco is combined with a simultaneous side-to-side motion resulting in an elliptical motion to increase the efficiency of breaking up the lens. With torsional ultrasound, the phaco tip is angled and moves in a circular oscillating motion that also aims to maximize cutting efficiency.
Both technologies decrease heat production and can result in clearer corneas postop. Traditional phaco is continuous, which means exactly what the name implies—energy is delivered the entire time the foot pedal is pressed.
Pulse mode is a power modulation that allows for automated alternating of phaco-on and phaco-off time. The concept to understand is that the number of pulses per second is independent of the duty cycle.
The number of pulses is set to the surgeons preference. Burst mode is a power modulation in which the time interval between each burst is dependent on depression of the foot pedal. The farther the foot pedal is pressed, the shorter the phaco-off time becomes, and maximum foot pedal depression is equivalent to continuous phaco. Hyperpulse and hyperburst extend the range of programmable settings.
Traditional pulse mode is limited to 20 pulses per second, but hyperpulse can allow for greater than pulses per second. Similarly, hyperburst can be programmed to a very short burst of 4 ms compared to regular burst mode of about 80 ms. Both options can be helpful in limiting phaco energy and heat delivered. As surgeons, we must change our settings depending on the type of case. I have found that this mode generates very little heat and allows for very clear corneas on postop day 1, even with a supracapsular approach, which is what I favor for a soft lens.
In all cases, the goal is to phaco only when there is complete occlusion at the phaco tip, to minimize unnecessary energy. Understanding the options for power modulation allows a surgeon to decrease energy production, reduce endothelial cell loss, resulting in more efficient surgery, clearer corneas, and ultimately better patient outcomes.
She can be contacted at Lisa. Park nyumc. Flow with a peristaltic pump refers to how fast that wheel is turning, which in turn indicates how fast fluid is moving through the device. If you occlude the tip, the pump still turns. No fluid can enter, so the vacuum in the line starts building. One question many people ask is if you do not have an occluded tip, do you get vacuum?
Although there will never be a maximum vacuum in this situation, you will still get some vacuum. You will see the vacuum go up by increasing the ramp speed, and your tip is a point of resistance. Although many cataract surgeons like peristaltic pumps, there is the concern that you will have uncontrolled vacuum pulling things forward. If this occurs, the flow is too high. You have to lower your flow rate or lower your vacuum. I tend to think of flow and vacuum as working independently of each other, but they also work together.
Think of flow as speed. The faster that pump turns, the faster fluid has to go through. If the procedure seems to be taking too long, maybe you need to turn up the flow.
If surgery is going too fast, lower the flow rate so you in turn lower the speed. Think of vacuum as akin to grip. If things keep falling off, you need to increase your grip.
Flow has a lot to do with distal followability. On the other hand, the problem with too much vacuum is surge, which is a dangerous possibility. One thing to help prevent this is an anti-surge algorithm. Surge is very much dependent on the level of vacuum immediately before occlusion is broken. You have your tip, and your tip is occluded with the piece. If you have a vacuum of and that piece suddenly goes in, that is where you will want to minimize surge.
At different points during the case, such as when you need to impale the nucleus early on with chopping, high vacuum is very safe. You can turn it up to because if you get a little surge, there will not be any issues with the posterior capsule. Find out how to optimize safety and efficiency with IOP, vacuum, aspiration, phaco-tip motion, power modes, continuous irrigation, chopping, quadrant removal, polishing, viscoelastic, infusion fluidics, ultrasound, phaco burst, phaco pulse and other functions.
Surgeons typically set up parameters when they initially buy a new phaco machine. To get the most out of phaco, Dr. Yet, setting the ultrasound settings too low may result in capsular bag movement and zonular stress, difficulty with disassembly and using too much irrigation fluid during needlessly long surgeries. Figure 1. Continuous phaco power provides a predictable flow of energy that increases to a preset limit when you depress the foot pedal. She notes that longitudinal energy is the traditional phaco modality.
The phaco needle moves in a forward and backward motion, creating mechanical impact in a jackhammer fashion. Cavitation bubbles appear, implode and propagate energy waves, which break up the lens material. Increasing phaco power is achieved by increasing the stroke length. Continuous, Pulse and Burst You can also make phaco more efficient by modifying the timing or duration of ultrasound power, according to Dr.
The basic power settings available include continuous, pulse and burst modes. Figure 2. In phaco pulse mode, the time between pulses, known as the off time, allows the phaco needle to cool, reducing the heat and energy delivered into the eye. The ratio of the total phaco-on and phaco-off time is expressed as a percentage. A percent duty cycle, for example, means that the power is on half the time and off the other half, according to Dr. However, she adds, you can alter the duty cycle to change the on-and-off times.
For example, you can program your machine to provide a percent duty cycle, which results in 20 milliseconds of energy followed by 80 milliseconds of no energy in each cycle. Figure 3. In the phaco burst mode, bursts of equal levels of energy are delivered more rapidly as the pedal is depressed. Park emphasizes selecting the right pulse rate and duty cycle for the right circumstances. During sculpting, for example, energy creates a groove and, therefore, higher pulse rates tend to work better because the narrower time intervals between pulses produce a smoother delivery of ultrasound energy.
For quadrant removal, she says, a lower duty cycle tends to be a better choice most of the time because a long interval between pulses allows for the aspiration of nuclear fragments. Burst, the third mode, also helps in special situations. The more the pedal is depressed, the shorter the off period is between each burst. In other words, the bursts of energy are delivered more rapidly as the pedal is depressed. At the maximum point of depression, the time between bursts becomes infinitely smaller and essentially constitutes a continuous delivery of energy.
The vacuum and fluidics of the phaco machine are used to aspirate the cataract fragments and give small bursts of power only when necessary, she notes. Long pulse mode is a to millisecond pulse duration. Remember Your Parameters Dr. Auran, also the surgical curriculum director for the Columbia University ophthalmology residency program, says intelligent use of phaco parameters is essential.
Increased IOP also stabilizes the chamber, especially in the presence of high aspiration and vacuum or when leaking incisions are involved. We can minimize post-occlusion surge in these situations. Auran points out that, according to in vitro data, increasing the IOP to as high as mmHg in the Alcon Centurion system can make the machine more efficient.
Auran notes that vacuum varies when the phacoemulsifier is turned on, requiring you to use vacuum for aspiration only. Quick taps of the tip will advance the tip deeper into the nuclear fragment, enabling a firmer hold. Auran says you can ensure the best use of vacuum to hold a lens, capsule or iris against the instrument tip.
Increasing vacuum can also increase phaco efficiency in some machines, to some extent. Meanwhile, a very high vacuum setting decreases efficiency, 6 but does allow for the aspiration of soft and medium pieces of the nucleus, which can be aspirated with minimal or no phaco power, notes Dr.
Meanwhile, when you increase aspiration you increase phaco efficiency, Dr. Auran points out, noting that high aspiration can help with sticky material, such as the epinucleus and cortex, and for viscoelastic removal. However, high aspiration can also be risky. Appreciating Variable Power Dr. Auran says increasing phaco power generally increases efficiency. Higher power can increase the risk of corneal injury, wound burn, iris damage and capsular rupture.
Are there any other approaches to increase efficiency? One example, Dr. Park points out, is limiting power to prevent excessive heat build-up. She also urges you to use the innovations in phaco technology that augment longitudinal phaco, when indicated.
Remember that transversal ultrasound helps emulsify the nucleus in more than one direction, increasing cutting efficiency. The main advantage of torsional phaco is increased energy efficiency, but the main disadvantage is significant tip movement. Note that transverse and torsional phaco are proprietary. Figures 4 and 5. When performing an anterior vitrectomy during cataract surgery, James D.
Auran, MD, recommends removing the vitreous at 4, cuts per minute and aspirating fluid in the third pedal position. For lens removal with the vitrector, make careful adjustments to draw the lens pieces away from vitreous without aspirating the vitreous while slowing the cut rate to to cuts per minute, he says.
This opens the cutter port enough to produce sufficient aspiration and vacuum to engage the lens pieces. Meanwhile, remember that specific phaco units perform differently. Auran adds. The Whitestar Signature Pro, when used with longitudinal power and a degree bevel straight tip, increases efficiency up to percent. Efficiency is optimal at 90 percent power in the transverse mode with a cm bottle height and vacuum at mmHg. Auran explains how phaco modes can help keep your surgeries safe, efficient and responsive to the needs of varied patients.
Unlike torsional or transverse power, longitudinal power will likely draw the nucleus toward the tip. The chop mode is for holding the lens, he continues. Some surgeons go right to quad, drawing pieces of the lens toward the phaco tip, relying on increased aspiration and vacuum and as much phaco power as needed.
The torsional or transverse modes, less likely to repel nuclear particles, might be best. Epinuclear settings are for handling the rubbery outer layer of the nucleus, again with moderate to high vacuum and aspiration, as needed, with minimal or no phaco power and high IOP to push the capsule posteriorly, as appropriate, he notes. To prevent this, elevate the IOP, pushing the capsule bag back and making it taut.
When engaging and stripping cortex in the periphery, use moderate vacuum and high aspiration. Once cortex has been drawn into a safe area in the center at the iris level, increase aspiration and vacuum to aspirate cortex. Polish is best used with a silicone tip, according to Dr. It involves very low settings while you keep the pressure high and capsule taut. Very low vacuum and aspiration are indicated to gently remove cells while minimizing the risk of aspirating capsule material.
Viscoelastic can be used to viscopolish the lens capsule.