EyeWorld India March 2021 Issue

REFRACTIVE 30 EWAP MAR C H 2021 by Liz Hillman Editorial Co-Director The many considerations of astigmatism management Contact information Berdahl: john.berdahl@vancethompsonvision.com Lee: bryan@bryanlee.pro Ristvedt: deborah.ristvedt@vancethompsonvision.com Swan: russell.swan@vancethompsonvision.com Wiley: wiley@cle2020.com This article originally appeared in the December 2020 issue of EyeWorld . It has been slightly modified and appears here with permission from the ASCRS Ophthalmic Services Corp. M anaging astigmatism at the time of cataract surgery is a weighty topic with many variables. What technology to measure astigmatism— power and axis? How many measurements to take for reliability? How to ensure accuracy and consistency of measurements? 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 measurements. One thing they all had in common was the use of multiple devices. Dr. Swan said he obtains a Placido-based topography (Nidek OPD) and Scheimpflug topography (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 Placido 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 astigmatism and a standard topography to assess the quality of the astigmatism. Dr. Lee also gets three sets of measurements—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 “astigmatism can be from the cornea and the lens itself, 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 keratoconus. 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 topography to see if the astigmatism is regular or irregular and on the topographer there is a Placido