EyeWorld Asia-Pacific December 2015 Issue

10 December 2015 EWAP FEATURE the point of least resistance.” Phaco incision ‘burn’ Phaco incision “burn,” Dr. Chan said, is a rare complication in phacoemulsification—“burn,” in quotes, she said, because there is no true oxidation occurring in the tissue. “What you’re seeing is corneal incision contracture induced by heat generated by the ultrasound friction,” she said. “It’s an acute reaction in the corneal collagen when the incision temperature reaches about 60°C. Incision burns can cause visible corneal striae, difficulty closing the incision, and iris prolapse due to poor wound apposition. “This results in induced irregular astigmatism and overall loss of best corrected visual acuity,” she said. “Basically not great for the patient.” Small burns can be managed with a suture—“as it epithelializes there’s no significant damage.” However, if the burn covers a large area and does not epithelialize properly even after placement of a bandage contact lens, the patient will need a patch or glued graft. “We did a survey study several years ago and invited American and Canadian surgeons to respond to a survey,” Dr. Chan said. 5 The study investigated the risk factors for incision burn. “In terms of actual data that was usable, 842 cataract surgeons essentially reported on close to a million surgeries, and 341 incision burns were reported which was an incidence of 0.037%.” In a multivariate analysis, Dr. Chan and her colleagues found significant associations between incision burns and surgical volume, surgical approach, and the type of ophthalmic viscosurgical device (OVD) used. “Surgical volume was the most significant predictor, and the incidence was inversely associated with the surgeon’s surgical volume,” Dr. Chan said. “In fact there was a 40% decrease per doubling of the volume, and this was statistically significant. Now, that’s not to say that just because the more you do the less wound burn you’ll probably have, it’s really more that surgeons doing high volumes probably have an efficiency associated with such a busy surgical practice and have developed an approach that requires a minimal amount of ultrasound energy.” In terms of surgical approach, divide-and-conquer, carousel techniques, and stop-and-chop approaches to nucleus disassembly had an adjusted incidence of incision burn “at least twice that of other chop methods such as vertical or horizontal chop approaches.” In terms of OVD, Dr. Chan said that Healon 5 (Abbott Medical Optics, AMO, Abbott Park, Ill.) was statistically worse compared to all the other OVDs. “You can see a rate of 0.197% from the 14 surgeons who reported 32 incision burns out of the over 16,000 surgeries that were done.” In vitro OVD heat studies showed Healon 5 to be highly exothermic when ultrasound is introduced through it. In addition, the OVD’s high viscosity can block the fluid flow preventing the cooling of the phaco probe tip. “However, it’s interesting that Viscoat [Alcon, Fort Worth, Texas], which is a dispersive agent, has a low viscosity but is actually as or more exothermic than Healon 5,” Dr. Chan said. “Healon GV [AMO], which is a cohesive agent, has high viscosity but is minimally exothermic. So depending on how exothermic the OVD is makes a difference.” Dr. Chan said that incision burn can be prevented using a technique that she called “OVD cleanup”—clear away all the “fluff” that’s created in the area anterior to the nucleus prior to proceeding to the next step. “Essentially what you’re doing is you’re aspirating as well the exothermic OVD that overlies that central area where you will be carrying out most of your phacoemulsification,” Dr. Chan said. “Therefore, the ultrasound energy is now through a fluid- filled cavity instead of an area that’s tightly packed with an OVD. Secondarily, this actually helps you delineate the edge of the rhexis and helps you visualize the nucleus’s anterior surface better, which allows you to bury deep enough into your lens to get a good crack if you’re using chopping methods.” It is important, she said, to recognize a wound burn as soon as it begins to develop. “If you recognize it, you can continue with your case cautiously,” she said. “Using continuous ultrasound in sculpt mode is typically when this would happen because you’re on linear ultrasound and ultrasound energy is extremely high.” Non-linear phaco technologies such as OZil (Alcon) or ELLIPSE (AMO) technology is a little better because they use less phaco power. “Vertical or horizontal chop techniques are also excellent,” she said. “You can still continue with the case using mostly chop techniques, and when you’re eating up the rest of the nucleus make sure you’re not flooring your pedal too hard. “In the end you can put the suture in just to ensure that your wound closes well.” For dense lenses, there is always the option of extracapsular cataract extraction, a procedure that Dr. Chan said has been modified into sutureless manual small incision cataract surgery. In North America, where fewer and fewer ECCEs are being performed, “it’s becoming a lost art amongst our residents,” Dr. Chan said. Nonetheless, the technique is “definitely still a good option for dense, mature cataracts.” “There’s really no difference in outcomes when you compare it to phacoemulsification,” Dr. Chan added. “In fact, there’s shorter operating time and significantly lower costs with manual small incision cataracts.” Dr. Chan’s take home points were: when dealing with a dense cataract, be cautious, know that there is a higher risk for incision burns. If it does happen, it must be diagnosed early, ultrasound should be used very efficiently, with chop techniques used primarily. Remember that OVDs are exothermic, so avoid continuous ultrasound through an OVD-filled anterior chamber, and aspirate some of that OVD before you’re using ultrasound energy to the max. “Let’s all aim for 0% incidence,” she said. “I understand the exothermic CSCRS - from page 9