Eyeworld

EW CATARACT 40 October 2016 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—sig- nificantly less surge and slowing ev- erything 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 occlud- ed 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 pro- fessor, Baylor College of Medicine, of the steps and maneuvers have different primary phacodynamic objectives." Sculpting, he said, is all about cutting efficiency, which fea- tures 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 vacu- um, 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-longi- tudinal phaco modes to maximize followability. "With mobile nuclear frag- ments, 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 epinu- cleus 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. 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 repel- ling force of the tip, which may kick away loose pieces of nucleus." Dr. Chang said that non-longi- tudinal 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 unop- posed by repelling axial phaco tip excursion. Dr. Chang recommended a phacodynamic game plan for chop- ping in which different packages of machine parameters are used for the different component steps. "Each the feeling of hooking and cradling the nuclear equator with the hori- zontal chopper tip while it is in the capsular bag." "Next, use stop and chop to transition to intracapsular chop- ping … you've already cracked the trenched nucleus in half so you only have to chop the radius of the nucle- us rather than the full diameter. Because you've sculpted that little trench, it automatically gets you to position your phaco tip at a much deeper level than with an unsculpt- ed, untrenched nucleus," Dr. Chang said. "Finally, stop and chop is the first time that you're actually placing the horizontal chopper peripheral- ly under the anterior capsular rim, hooking the equator of the nucleus, turning the chopper tip so that it's vertically oriented, and then chop- ping directly toward the phaco tip, which is your chopping board," he continued. "The key is keeping both your chopper and your phaco tip deep, and to have as much nucleus in the path of the horizontal chop- per as possible." Once adept with this, the surgeon can transition to "non-stop" chopping by eliminat- ing the sculpting and initial trench. "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 Moving continued from page 38

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