Eyeworld

EW CATARACT 36 February 2017 by Ellen Stodola EyeWorld Senior Staff Writer to prevent post-occlusion surge. "I use single burst mode to deeply impale a dense nucleus for chop- ping," Dr. Chang said. This ensures tip occlusion so that the maximum vacuum is achieved. However, once the nucleus is chopped into multi- ple small fragments, he switches to non-longitudinal phaco modulation to reduce the repelling force of the tip and to improve followability. One final piece of advice is that with a dense nucleus, it is important to first aspirate some of the dispersive OVD lying directly over the central nucleus, Dr. Chang said. Otherwise, the admixture of dispersive OVD with brunescent nuclear emulsate could occlude the phaco tip, leading to a wound burn. With a soft lens, Dr. Oetting said divide and conquer is tricky. You either want to prolapse the soft lens up so it's soft enough to suck out, or you can do a chop where you essen- tially use no vacuum, and the idea is to do a horizontal chop with no settings at all. The main thing is you want to be careful with occlusion and vacuum, Dr. Oetting said. EW Editors' note: Dr. Chang has financial interests with Abbott Medical Optics (Abbott Park, Illinois), Transcend Medical (Menlo Park, California), Mynosys (Fremont, California), PowerVision (Belmont, California), and LENSAR (Orlando, Florida). Dr. Oetting has no financial interests related to his comments. Contact information Chang: dceye@earthlink.net Oetting: thomas-oetting@uiowa.edu roller balls rotate, the more mil- liliters of fluid pass through the tubing. With the peristaltic pump, the surgeon sets the aspiration flow rate, and the vacuum is not directly controlled but is a function of the resistance to flow. These machines have a vacuum setting that does not directly set the vacuum, but instead sets the vacuum point at which the pump should stop due to flow resistance. Vacuum-based venturi pumps have a fixed chamber with air flow- ing above to create a pure vacu- um-based pump. With the venturi pump, the physician directly sets the vacuum, and the aspiration flow is a function of the resistance. For exam- ple, most pumps used for posterior vitrectomy use venturi pumps so that the surgeon can set the vacuum directly, which keeps the vacuum stable despite frequent occlusion of the vitrectomy cutter. Dr. Chang reviewed the phaco- dynamic strategy for a dense nucleus. If you are sculpting, you need some aspiration flow to clear the emulsate, but you don't want too high a vacuum. Otherwise, the peripheral epinucleus tends to rush into the phaco tip toward the end of the sculpting stroke when the tip slows down and occludes. To chop, you want to maximize your grip of the nucleus with high vacuum, espe- cially with vertical chop where the downward chopping motion tends to dislodge the fragment from the tip. However, as you get to the last fragments, and more of the posterior capsule is exposed, it is important to reduce the vacuum by about 50% While longitudinal ultrasound power can push pieces away from the tip, power modulation strategies (e.g., pulses with less on than off time) can help nuclear material flow smooth- ly to the tip. Some systems employ torsional or rotational energy, which goes sideways and pushes away mate- rial less and adds to the efficiency of the procedure. Modern systems allow flexibility in how ultrasound power is applied while in position three of the foot pedal. Dr. Oetting explained that the simplest is continuous when the power is on whenever the pedal is in position three. The farther down in position three, the more power is delivered. A pulse mode is a com- mon modulation variant where the power is on for a set time and then off for a set time. A common pulse variant is the "hyperpulse" with a high frequency pulse with a long off time to keep the phaco tip cool. The final common modulation variant is a burst where the power is delivered for a set time with a set power. The farther you go into position three, the less time comes between the bursts. If you fully engage position three in burst mode, the power be- comes continuous. Dr. Chang and Dr. Oetting then discussed machine settings, and spoke about handling different types of lenses. Peristaltic pumps are flow based, and venturi pumps are vacuum based. Dr. Oetting described peri- staltic pumps as typically having the tube against rotating roller balls, which set the rate of fluid passing through the tubing. The faster the The final webinar in the series "puts it all together" T he final webinar in the ASCRS Young Eye Surgeons (YES) Clinical Committee's PhacoFUN series took place in late November on the topic of "Phaco FUNdamentals: Putting It All Together." Zaina Al- Mohtaseb, MD, Houston, moderat- ed the session, with Jeremy Kieval, MD, Lexington, Massachusetts, as facilitator. David F. Chang, MD, Los Altos, California, and Tom Oetting, MD, Iowa City, Iowa, served as panelists. The webinar sought to review some of the basic phaco parame- ters like aspiration, vacuum, bottle height, and phaco power. It also covered optimizing parameters for intraoperative floppy iris syndrome (IFIS) and post-vitrectomy eyes. Dr. Chang highlighted some of the basics of phaco settings. "For a peristaltic pump, the two aspiration variables that you're controlling are flow rate and vacuum limit," he said. Flow rate determines the speed of how fast things are happening within the eye. Vacuum determines holding power—how strong the oc- cluded phaco tip is able to grip lens material. If things are happening too quickly, you can reduce the aspira- tion flow rate, Dr. Chang added. If you need more holding power, you can increase the vacuum as long as you don't start to get too much post-occlusion surge. Longitudinal (axial) is the classic phaco power, Dr. Oetting said. It has both advantages and disadvantages. Phaco fundamentals discussed in ASCRS webinar anterior segment surgery residents) rotating through the facility every year. The surgical time reported in the current study may also vary depending on the documentation accuracy of the circulating nurse, lack of support from the surgical OR nurse (non-ophthalmic nurse), and the time needed to load the IOL into the injector, which is done by the surgeon at the VA facility in D.C. Data revealed that second-year residents performed 698 phaco and IOL surgeries in 52,964 minutes, while third-year residents performed 1,358 phaco and IOL surgeries in 78,321 minutes. "Teaching surgery to residents helps train the next generation of ophthalmic surgeons and assists residency programs, but also decreases VA OR time efficien- cy," Dr. Magone said. "In our study, the number of potential phaco surgeries that could be performed by an attending surgeon within the available OR time decreased by 41% secondary to intraoperative resident teaching. However, patient safety and visual outcomes are not compromised by resident teaching as shown by our results." Another recent VA study reported favorable 5-year outcomes resulting from resident-performed cataract surgery as well. 2 "It is heartening to see that this essential training of our future ophthalmologists is also associated with excellent patient outcomes," she said. EW References 1. Evaluation of Cataract Surgeries and Outcomes in VHA Facilities. 2013 OIG Report 11-02487-158. 2. Payal AR, et al. Outcomes of cataract sur- gery with residents as primary surgeons in the Veterans Affairs Healthcare System. J Cataract Refract Surg. 2016;42:370–84. Editors' note: Dr. Magone has no finan- cial interests related to her comments. Contact information Magone: maria.magone@va.gov Cataract continued from page 35 Webinar reporter

• Cover