Eyeworld

EW CATARACT 65 February 2018 by Liz Hillman EyeWorld Staff Writer dard methods of calculating net cor- neal refractive power are often inac- curate, and estimated lens position is difficult to predict, Dr. Vann said. ASCRS offers an IOL power calcu- lator for eyes that have had LASIK, PRK, or RK. This tool considers all of the published nomograms that account for these factors, Dr. Vann said, adding that intraoperative ab- errometry can also be a helpful tool to measure the refractive state of the eye in an aphakic mode. The following is a selection of audience questions. Question: Since both the equivalent K reading (EKR) and Barrett Toric Calculator take into account the posterior cornea, is using the EKR in Barrett double correcting for posteri- or cornea? Dr. Wang: Yes, you are correct. Question: Do you compare different formulas and compare IOL calcula- tors and choose the IOL power that will be an acceptable outcome given all formulas or will you weigh one formula over others? Dr. Hill: As I mentioned, the newer formulas from this century, like Hill-RBF, Barrett Universal II, and Olsen, do a very good job. If you have access to the Hill-RBF and Barrett Universal II, I would look at those two and weigh them more heavily because they have the better outcomes. Question: Does IOLMaster have the Barrett Universal II and Hill-RBF formulas in it? Follow-up to an ASCRS webinar provides insight on previously unanswered questions from attendees A n ASCRS webinar spon- sored by the IOL Power Calculation Subcommit- tee in November 2017 drew an audience of more than 200 attendees who were interested in learning more about optimizing their calculations and outcomes. As Warren Hill, MD, East Valley Ophthalmology, Mesa, Arizona, and chair of the IOL Power Calculation Subcommittee, put it in an inter- view with EyeWorld, "We as anterior segment surgeons are judged by our patients and our peers by our refrac- tive outcomes; it's one of the single most important things that we do." Dr. Hill, moderator of the we- binar, was joined by Li Wang, MD, PhD, associate professor, Baylor College of Medicine, Houston, and Robin Vann, MD, assistant pro- fessor, Duke University School of Medicine, Durham, North Carolina, to discuss the role of the surgeon, accuracy standards for IOL power calculations, validation criteria, IOL power selection methods, and considerations for cases of high axial myopia, high axial hyperopia, astigmatism, and prior refractive surgery. In addition to the webinar's main presentation, Dr. Hill an- swered a variety of questions from attendees throughout. This article will answer questions that were not addressed during the webinar due to time constraints and repeat others that have wide applicability. Getting 90% of one's cases to within a ±0.50 D spherical equiva- lent is possible, Dr. Hill said in the presentation. In order to achieve this, Dr. Hill and his fellow panel- ists explained the importance of incorporating validation criteria and "[using] IOL power selection meth- ods from this century." Validation criteria, Dr. Hill explained, allows surgeons to look at their measure- ments and judge if they're likely to be correct. There are instrument-spe- cific validation guidelines that give physicians parameters for accepting values on a given machine. Dr. Hill provides downloadable vali- dation criteria for the IOLMaster (Carl Zeiss Meditec, Jena, Germany) and LENSTAR (Haag-Streit, Köniz, Switzerland) on his website, www. doctor-hill.com. IOL power calculation methods recommended during the webinar were the Barrett Universal II formu- la and the Hill-RBF method. These two approaches, Dr. Hill said, give surprisingly similar results, despite using entirely different mathemat- ical methods. If you are limited by your biometer to older vergence formulas, Dr. Hill said the Holladay 1 is advised, applying the Wang- Koch axial length adjustment for very long eyes. In eyes with high axial hyperopia, Dr. Vann discussed a recent JCRS study that showed the best formulas for these eyes are the Holladay 1, Holladay 2, and Hill- RBF. For toric IOL calculations, Dr. Hill said it's important to validate your autokeratometry measure- ments with a topographic axial power map. If the auto-Ks do not line up with the power distribu- tion displayed on the topographic map, Dr. Hill said one should use a manual keratometer to calculate the power difference between the steep and flat meridians. He also said the Barrett Toric Calculator "has the most to offer," that surgeons should be striving to orient toric IOLs within 5 degrees or less of their in- tended target, and posterior corneal astigmatism should be considered. In cases where outcomes with toric IOLs miss the mark, Dr. Hill recom- mended using the Barrett Rx tool or astigmatismfix.com. Patients with prior refractive surgery pose a challenge for sur- geons in that it's more difficult to determine anterior power, the stan- Experts address questions from IOL power optimization webinar Webinar reporter continued on page 66 Personal experience Musculoskeletal health was under- scored early for Dr. Berdahl, who underwent a discectomy when he was 22 years old. "I am very careful of my posi- tion," Dr. Berdahl said. "The right side of my body, especially my shoulder, has a tendency to be lower than on the left, so I need to expand the right side of my torso by taking deep breaths and arching to the left. That helps anytime I experience lower back pain." Dr. Lindstrom has experienced many sports-related injuries over the years, especially from competitive ski racing. He advises using ice for acute pain, heat for chronic pain, and the best NSAID he has found is celecoxib 200 mg. He avoids opioids, even in the presence of significant post-surgical pain. Symptoms to watch for Among the symptoms Dr. Lindstrom suggested surgeons stay alert for as a warning of developing repetitive stress injuries are numbness and pain, which come first when there is a serious problem on the way. "The sensory nerves are on the outside of the nerve bundles," he said. "If you ignore reduced sensation and chron- ic pain, you may end up with motor damage that can be permanent." Dr. Berdahl suggested his fellow surgeons particularly watch for excessive fatigue at the end of a day in the OR, as well as feeling like it's hard to get in and out of the proper surgical position. EW Reference 1. Dhimitri KC, et al. Symptoms of musculo- skeletal disorders in ophthalmologists. Am J Ophthalmol. 2005;139:179–81. Editors' note: Dr. Lindstrom and Dr. Berdahl have no financial interests related to their comments. Contact information Lindstrom: rllindstrom@mneye.com Berdahl: johnberdahl@gmail.com Prioritizing continued from page 62

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