Eyeworld

74 | EYEWORLD | DECEMBER 2020 R EFRACTIVE by Liz Hillman Editorial Co-Director M anaging astigmatism at the time of cataract surgery is a weighty topic with many variables. What technology to measure astigma- tism—power and axis? How many measurements to take for reliability? How to ensure accuracy and consistency of measure- ments? What course of correction to take? EyeWorld spoke with five doctors—John Berdahl, MD, Bryan Lee, MD, JD, Deborah Ristvedt, DO, Russell Swan, MD, and William Wiley, MD—to get their take on these questions and more, finding that, for the most part, they have similar approaches. Measurements The doctors EyeWorld spoke with use a range of technologies to obtain astigmatic measure- ments. One thing they all had in common was the use of multiple devices. Dr. Swan said he obtains a Placido-based to- pography (Nidek OPD) and Scheimpflug topog- raphy (Pentacam, Oculus) as well as an optical biometry (Lenstar, Haag-Streit) measurement. Through these technologies he also is able to obtain a higher order aberration profile, a Plac- ido disc image to assess the mires, and a whole corneal thickness map. These technologies can help identify corneal aberrations, ocular surface disease, and irregular vs. regular astigmatism. Dr. Wiley uses the IOLMaster 700 (Carl Zeiss Meditec) and Pentacam, which he said allow him to understand the role of the total cornea—front and back—in the patient's astig- matism and a standard topography to assess the quality of the astigmatism. Dr. Lee also gets three sets of measure- ments—automated Ks, IOLMaster 700, and iTrace (Tracey Technologies) topography and aberrometry. He also said it's helpful to know the patient's old glasses prescription to estimate posterior corneal astigmatism. "You always are looking for consistency among the numbers to give you confidence in your IOL selection," he said. Dr. Ristvedt also said a glasses prescription is important to identify what a patient is used to wearing and if lens extraction will uncover more astigmatism. "I get picky on the Lenstar Ks to make sure the axis is within 3 degrees as we take multiple Ks," she said, adding later that, because "astig- matism can be from the cornea and the lens it- self, it's nice to compare multiple technologies." While all of the doctors mentioned getting corneal topography as part of the astigmatism assessment process, Dr. Berdahl said he doesn't think it's standard of care per se. "But I do think it's a good idea and almost necessary for premium IOLs. There can be subtleties on a corneal topography that indicate higher order aberrations that originate from the cornea, irregular astigmatism, or even kerato- conus. As we're trying to determine if a lens is going to be able to correct those problems, we need to understand if those problems exist in the first place," he said. The role of the ocular surface Several of the measurement and mapping technologies mentioned above can indicate an ocular surface issue for investigation, but Dr. Ristvedt discussed the importance of dry eye testing overall to ensure accuracy of astigmatic measurements. "We do tear osmolarity and InflammaDry [Quidel] and put it together with our slit lamp examination," she said. "We look at our topog- raphy to see if the astigmatism is regular or irregular and on the topographer there is a Plac- ido disc. That gives us so much information." One of Dr. Ristvedt's recent patients came in wanting a PanOptix trifocal IOL (Alcon), but some things on her measurements were not adding up and Placido showed blurred rings. "We treated her dryness and had her come back for repeat measurements. Not only did the power of astigmatism change but also its orien- tation," she said. "If I would have gone ahead with a premium lens, we would have been in trouble postop." Dr. Lee discussed how pterygium, anterior basement membrane dystrophy, and Salzmann's nodular degeneration could also impact astig- matic measurements. The many considerations of astigmatism management About the doctors John Berdahl, MD Vance Thompson Vision Sioux Falls, South Dakota Bryan Lee, MD, JD Altos Eye Physicians Los Altos, California Deborah Ristvedt, DO Vance Thompson Vision Alexandria, Minnesota Russell Swan, MD Vance Thompson Vision Bozeman, Montana William Wiley, MD Cleveland Eye Clinic Division of Midwest Vision Partners Cleveland, Ohio continued on page 76

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