Eyeworld

36 | EYEWORLD | SEPTEMBER 2022 Contact McCabe: cmccabe13@hotmail.com Schallhorn: scschallhorn@yahoo.com Reference 1. Schallhorn SC, et al. Effect of residual astigmatism on uncor- rected visual acuity and patient satisfaction in pseudophakic patients. J Cataract Refract Surg. 2021;47:991–998 Relevant disclosures McCabe: Alcon, Bausch + Lomb, Carl Zeiss Meditec, Johnson & Johnson Vision, LENSAR, Rayner Schallhorn: None ATARACT C continued from page 34 also said it's important to have an idea about the shape of the astigmatism, if it's irregular, indicating a complex cornea, or regular astigma- tism. "You don't have to get super sophisticated about that, but you do need a picture of the central curvature of the cornea that tells you whether the astigmatism is regular or not," she said. This can be determined with a topographer or even manual keratometry, looking for clear, sharp, and orthogonal mires. Having this basic information, Dr. McCabe said, helps set sur- geons up for successful astigmatism treatment. Then you have to decide how to treat. There are several reasons that many physicians lean toward putting in a toric lens, if it's indi- cated, she said. First, there is long-term stability and predictability of toric IOLs. "We don't have to factor in healing of the arcuate incision, heal- ing that's individual to the patient," Dr. McCabe said. Second, this option doesn't impact ocular surface health, while arcuate incisions and cut- ting through the corneal nerves can worsen dry eye in the postoperative period. For these reasons, Dr. McCabe said she uses a toric lens when indicated, however, she noted that, in the U.S., low power torics are not avail- able. "There are lower levels of astigmatism that I still think are important to treat, especially if we're putting in a diffractive optic, and in those cases where it's a lower level of astigmatism, I'll do arcuate incisions," she said. "I think allowing patients to have the best quality of vision at distance is what they find to be most important," she said. "We can provide an increased independence with excellent dis- tance vision for most patients, and that funda- mentally depends on accurate and universally applied astigmatism correction." The effect of residual astigmatism was the subject of an extensive study 1 in which Dr. Schallhorn participated, looking at different amounts of astigmatism to determine what effect they have. "Above a relatively low level, you should consider addressing it to achieve the best unaid- ed postoperative vision and maximize patient satisfaction," he said. Dr. Schallhorn's study found that even low levels of postoperative astigmatism can impact unaided vision and patient satisfaction after surgery. This includes 1 D or 0.75 D, but even down to 0.25–0.5 D. He called this conclusion a "wakeup call" for physicians to pay closer at- tention to corneal astigmatism and how to best address it. A surprising, incidental finding from Dr. Schallhorn's study was that leaving patients slightly hyperopic led to slightly better outcomes and patient satisfaction. "What it showed, which needs to be studied in greater detail, was that a low level of hyperopia resulted in better uncorrected vision and happier patients than if you leave those patients slightly myopic," Dr. Schallhorn said. The important caveat is that it was in patients who wanted good distance vi- sion in that eye; of course, this is not for patients in whom you're targeting myopia. In those patients where the physician wants to hit zero refractive error and give the best un- corrected distance vision, the findings from the study suggested that leaving patients slightly hyperopic is better than leaving them slightly myopic, he said, further clarifying that this is in reference to when the surgeon is deciding between lens power options with half diopter in- crements in which the estimated postop refrac- tion straddles emmetropia. Previously, he would default to leaving the patient slightly myopic. He reiterated that this needs to be investigated further to understand in greater detail what it means and how should it drive practice. The size of the study was its strength, Dr. Schallhorn said. It requires large sets of data to accurately assess patient satisfaction and patient-reported outcomes because of the inherent variability in patient responses. Dr. McCabe said that she usually aims for as close to plano as possible. "I've found that allows the patient to have the best quality of vision," she said. "Unfortunately, right now, we don't have a way of targeting in less than half diopter increments of power." Dr. McCabe said that when it's within a half diopter, she generally will target closest to plano or a little on the my- opic side, but she added that there are certain optics that work better with a little residual hyperopia, like the Synergy (Johnson & Johnson Vision).

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