EyeWorld Asia-Pacific December 2016 Issue

37 EWAP CATARACT/IOL December 2016 “Start by hooking the nasal nuclear equator with the horizontal chopper tip, and then impale the nucleus proximally with the phaco tip. By keeping both tips deep, you will bisect the nucleus,” he said. “This game plan for transitioning means that you master the component skills and steps in reverse order—starting with the easiest steps first.” Dr. Chang and Dr. Oetting then discussed the basics of phaco settings. Dr. Chang said that for a peristaltic pump system, aspiration flow rate determines the speed at which things happen, while vacuum provides the gripping or holding power. “It is important to remember that the more longitudinal phaco power you are using, the greater distance the phaco tip moves back and forth in the axial direction,” he said. “Therefore, as you increase the power, you are increasing the repelling force of the tip, which may kick away loose pieces of nucleus.” Dr. Chang said that non- longitudinal power modulation improves nuclear followability and reduces chatter by replacing axial phaco tip movement with either torsional or elliptical movement. Pulse mode cuts true phaco time in half and provides momentary periods when vacuum and aspiration are unopposed by repelling axial phaco tip excursion. Dr. Chang recommended a phacodynamic game plan for chopping in which different packages of machine parameters are used for the different component steps. “Each of the steps and maneuvers have different primary phacodynamic objectives.” Sculpting, he said, is all about cutting efficiency, which features higher phaco power and lower flow and vacuum. When it’s time to impale the nucleus for chopping, Dr. Chang said to use a high vacuum, a higher flow rate, and to avoid continuous phaco power so as not to lose your purchase and grip. Dr. Chang said impaling the nucleus with continuous phaco power “is like stabbing fruit with a toothpick and then wiggling it—you immediately lose your purchase.” Quadrant and fragment removal require a high enough flow/vacuum to attract and secure free-floating fragments to the tip, and Dr. Chang recommended pulse and non-longitudinal phaco modes to maximize followability. “With mobile nuclear fragments, you want to minimize chatter and repelling pieces because that’s where we lose endothelial cells to mechanical bombardment with microfragments and chips,” he said. When it comes time for epinucleus removal, lower the vacuum to minimize post-occlusion surge. “The priority at this point is to avoid aspirating the exposed posterior capsule as the final fragments and epinucleus are removed,” Dr. Chang explained. Properly configuring phaco machine settings is important, but so is picking the appropriate phaco tip for chop. For those just starting out, Dr. Chang said he recommends a straight 20-gauge phaco tip, with a 30-degree bevel, rather than the 19-gauge phaco tip that is standard in many residencies. “You get major safety benefits with a smaller gauge phaco tip— significantly less surge and slowing everything down so that there isn’t as sudden an acceleration of aspiration when the tip occludes. This helps when trying to pluck crumbling softer fragments from the equatorial bag because the smaller tip is occluded without needing to penetrate as deeply, and the rate of aspiration is also slowed,” he said. “As wonderful as our modern phaco machines are, switching from a 19- to a 20-gauge phaco tip will do more to reduce your posterior capture rupture rate than any other machine feature, in my opinion,” Dr. Chang said. Now that the fictitious resident, Theresa, has reviewed her phaco basics and chosen the appropriate phaco tip, she’s ready to make her capsulorhexis. “Any considerations prior to making her rhexis?” Dr. Zavodni asked. The webinar’s facilitator, Zaina Al-Mohtaseb, MD , assistant professor, Baylor College of Medicine, Houston, said she would advise staining with trypan blue as it helps show where the anterior capsule actually is. For those just starting out with phaco chop, Dr. Al-Mohtaseb also said that doing both hydrodissection and hydrodelineation could be helpful. Hydrodelineation leaves the epinuclear shell for protection, while hydrodissection allows for good rotation of the lens epinucleus. Moving forward with the fictitious case, Dr. Zavodni said Theresa did indeed stain the capsule and performed both hydrodissection and delineation. Planning to horizontal chop, Dr. Zavodni asked where she should attempt to impale the nucleus at this stage. Dr. Chang offered his pearls for proper chopper placement, saying that with horizontal chop, the key is for the chopper tip to work within the epinuclear space. Though a “somewhat blind maneuver when you have to go just under the pupil margin,” causing the surgeon to worry about whether the chopper is inside or outside the bag, Dr. Chang recommended that transitioning surgeons inject a dispersive viscoelastic beneath the nasal anterior capsule to better visualize and increase the space between the peripheral endonucleus and the anterior and equatorial capsule. Dr. Oetting said he likes the idea of putting a little trench to help visualize where one should impale especially when getting started. For a pure phaco chop with no sculpting, he advised surgeons start about 2 mm short of the center of the lens and end up in the center or just past the center 100% occluded. “The number one problem that people have while they’re getting the chopper into position is letting go of the lens with the phaco needle. Usually, as people move in with the chopper, they pull back the phaco needle and lose their grip on the lens. The key is to move forward with the phaco needle as you move the chopper out so you don’t lose your grip on the lens. The main thing is you want to be in the area of the epinuclear/nuclear intersection and you want to make sure you’re under the capsule,” Dr. Oetting said. While horizontal chop is more appropriate for soft to medium lenses, denser lenses are more suited for vertical chop, Dr. Oetting said. When tackling a dense lens, Dr. Chang agreed and said that higher vacuum is much more important to increase holding power when chopping a dense nucleus. Dr. Zavodni concluded the webinar, offering a word of caution on his final slide: “Things happen in the anterior chamber for a reason. If they’re not responding the way you want them to, then change something.” Check out the webinar for more details about horizontal and vertical phaco chop, as well as two surgical case videos presented by Dr. Chang, at www.ascrs.org/ center-for-learning/video/phaco- FUN. You will need to register and log in to view this video. EWAP Editors’ note: Some comments have been slightly modified from the webinar for clarity. Dr. Chang has financial interests with Abbott Medical Optics (Abbott Park, Illinois) and Mynosys (Fremont, California). Drs. Al-Mohtaseb, Oetting, and Zavodni have no financial interests related to their comments. Contact information Al-Mohtaseb : zaina@bcm.edu Chang : dceye@earthlink.net Oetting : thomas-oetting@uiowa.edu Zavodni : zacharyzavodni@gmail.com Moving - from page 33