September 2018

CATARACT

Presentation spotlight
Breaking down the nucleus


by Stefanie Petrou Binder, MD, EyeWorld Contributing Writer


Soft slice

Surgeons should be comfortable mixing chopping approaches as the situation demands in this picture, a soft chop

Hard chop

Crack ergonomics: The long axis of the trench should bisect the surgeon’s instruments, cracking the nucleus from the bottom
Source (all): Richard Packard, MD

“In order to be a complete phaco surgeon, a variety of alternate techniques are required to deal with nuclei of differing densities: soft, medium, and hard.”
—Richard Packard, MD

Special nucleofractis approaches for different types of lens nuclei can improve surgical efficacy and help preserve the integrity of the capsule

Fresh advice from a seasoned surgeon can help keep surgeons on their toes. Speaking on nucleus management issues at the 22nd ESCRS Winter Meeting, Richard Packard, MD, Windsor, U.K., offered tactical pearls on how to use a variety of phacoemulsification approaches for nuclei of different densities.
“Now that we know how the phaco machine works, we have to understand how to best use it on the nucleus,” Dr. Packard said. “In order to be a complete phaco surgeon, a variety of alternate techniques are required to deal with nuclei of differing densities: soft, medium, and hard. When dealing with the nucleus, mechanical separation minimizes energy usage and chopping works best for dens nuclei. White nuclei can be brittle, and multiple separations may be needed to complete a chop. It is important to use power modulation to minimize energy dispersion during phaco. Surgeons should be flexible about varying their technique mid-case and have a range of options for the various types of nuclei.”

Divide and conquer

This four-quadrant nucleofractis technique is the mainstay of phaco surgery for many surgeons. When the surgeon begins to sculpt, it is important to minimize the movement of the globe by the correct use of power and by pressing the foot pedal without pushing the nucleus, which can disrupt zonules. With a Kelman tip, the surgeon’s hand needs to be held somewhat lower because of its curve, otherwise the tip might get occluded as the bevel is easily buried in the nucleus. Lowering the hand is easier when operating temporally, but when operating superiorly, the surgeon needs to extend the patient’s neck, dropping the head a bit, to gain good access to the eye over the brow.
“The important thing with sculpting is to keep the bevel exposed to avoid occlusion, which will cause the nucleus to move forward.” Dr. Packard said. “We want smooth passes. For trainees, I set the ultrasound power at 30–70% on the Infiniti and Centurion machines [Alcon, Fort Worth, Texas]. You need to be aware of the diameter of the phaco tip and depth of the nucleus to create the trench at an appropriate depth. One of things I encourage to help limit pushing the nucleus is to preset a power range so that as soon as foot position 3 is reached, power is engaged. Also, you want to lift the phaco tip after the center of the nucleus is passed to prevent sculpting through the nucleus to the other side. This is particularly important in softer cataracts with relatively little density.”
Cracking the nucleus needs the right ergonomics. The long axis of the trench should bisect the surgeon’s instruments, which are positioned at the bottom of the trench. “You are going to go down to the bottom of the trench and separate, but you need to push back though before pushing sideways so it cracks from the bottom, and allow time for the crack to propagate, especially with harder cataracts. To get a good crack in the nucleus, you want an equal and opposite pull on either side,” he explained.
To remove segments, Dr. Packard buries the phaco tip at minimal ultrasound power and allows the vacuum to build. The sound from the machine lets you know when you’ve reached maximal vacuum with full occlusion. Then the surgeon can pull segments centrally, for removal, in the safe area in the deepest part of the anterior chamber. This is repeated in each of the quadrants.

Chopping

“I use multiple chopping approaches, often mixing them as the situation demands,” Dr. Packard explained. “Each approach breaks up the nucleus with as little use of power and greatest use of mechanical disassembly and fluidics as possible. However, soft cataracts present certain problems. I think the phaco prechop is a good way to approach soft nuclei. You need to fill the anterior chamber with viscoelastic, do your 5 mm rhexis and full nuclear mobilization, and refill the anterior chamber with viscoelastic to provide a firm base to push the prechopper against. Push the prechopper toward the center of the nucleus and separate the blades several times until the nucleus splits. Then, turn the nucleus to repeat and remove segments with minimal power. The ‘soft slice’ technique is a different approach and is effective for up to 2+ nuclei.”
Here, the nucleus is sliced from the periphery to the center using a device like the Mackool iris repositor, which is blunt and has a short shaft. After each slice is completed, the segments can be separated until the nucleus is in four pieces, at which point it can be removed with minimal use of ultrasound power.
Phaco chop allows for fast and safe surgery, especially for hard cataracts, that need far lower energy levels in the eye due to the greater use of mechanical division, producing clearer day 1 corneas because of the lower energy use. There are two basic techniques, horizontal and vertical chopping, which can be mixed and matched.
“Horizontal choppers tend to be longer with a blunt end and often with a blade on the inside edge. Vertical choppers have shorter tips, often with a point. I use my own, which has a blade on the inside also. These differences reflect the way in which the two techniques are used,” Dr. Packard explained. “Horizontal chopping is very much a two-dimensional maneuver. You embed the phaco tip, then take the chopper out to the periphery of the nucleus and slide it over the nucleus, bringing the two instruments together and separating into segments. You can chop up the nucleus as many times as you like, but this is especially important with a hard cataract, which will enable you to use less power. Vertical chopping is a three-dimensional maneuver because you are lifting at the same time as you are chopping and separating.” The sharp vertical chopper is embedded in the nucleus near the end of the phaco tip, which has been buried in the middle of the nucleus.
Dr. Packard recommends either a sculpt vacuum for medium nuclei or high vacuum for hard ones with vertical chop. Minimal vacuum is required for a horizontal chop. Medium cataracts are best broken down with a soft chop technique. To avoid going straight through a medium nucleus but obtaining an adequate hold to chop, he recommends using a relatively low, sculpting vacuum setting of 75 mm Hg to bury the phaco tip. Once the vacuum builds enough to gain purchase and reach full occlusion, chopping can begin from the periphery toward the center of the nucleus.
Hard cataracts entail certain surgical considerations due to the lack of a red reflex and the possibility of fibrotic capsules or tense and swollen capsular bags. “There can be a small, mobile, often hard nucleus, or a large, dark, and hard nucleus, especially in older patients. The effect of advanced cataract on other ocular tissues is important to understand,” Dr. Packard said. “Hydrodissection of hard nuclei is usually easy, as there is less cortex holding the nucleus. White chalky cataracts are usually brittle and easy to chop. Multiple separations are important with dense brown cataracts, using high vacuum with the phaco tip well buried to give good traction on the nucleus. Moderate flow will control nuclear pieces and avoid turbulence that might shoot pieces against and damage the endothelium during segment removal. The posterior plate can be quite rubbery and needs to be broken down carefully. Usually, there is no epinucleus in these cases, but the posterior capsule still needs to be protected. The use of a dispersive viscoelastic throughout nuclear removal will protect both the endothelium and the posterior capsule. A modified soft shell technique is used whereby the dispersive OVD is used at the outset to fill the eye. After hydrodissection, the cohesive OVD is injected onto the top of the anterior capsule to push the dispersive against the endothelium. At the beginning of phaco, the cohesive is aspirated before using any ultrasound power. This will help to avoid wound burn. Using the dispersive OVD above and below the nuclear pieces will protect the ocular structures and hold these pieces in place for easier removal and less turbulence.”

Editors’ note: Dr. Packard has no financial interests related to his comments.

Contact information

Packard: mail@eyequack.vossnet.co.uk

Breaking down the nucleus Breaking down the nucleus
Ophthalmology News - EyeWorld Magazine
283 110
220 175
,
2018-09-03T15:14:02Z
True, 9