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4 Reducing pseudophakic ametropia to drive improved refractive IOL outcomes maximize patient satisfaction and quality of vision, the postop refractive error needs to be minimized. "The closer to zero residual refractive error, the higher the satisfaction, and the better the quality of vision," said Dr. Schallhorn. Developing intraoperative strategies to manage pre-existing astigmatism About 22% of patients scheduled for cataract surgery have pre-existing corneal astigmatism of greater than 1.25 D, ac- cording to William B. Trattler, MD, Center for Excellence in Eye Care, Miami, while 64% will have corneal astigmatism of 0.25–1.25 D. Since astigmatism is so com- mon in patients scheduled for cataract sur- gery, it is important to consider the various treatment options available to help mini- mize astigmatism postoperatively. Once patients with significant astigma- tism are identified, the condition can be addressed intraoperatively with a variety of approaches, including astigmatic kerato- tomy (AK) or limbal relaxing incisions (LRI)—which can be performed with a blade or a femtosecond laser. Alternatively, toric intraocular lenses can be used to effectively address moderate to high levels of astigmatism. Each approach comes with a specific set of considerations. Toric IOLs have limited cylindrical power gradations and address the corneal problem on the lentic- ular plane. AKs or LRIs using a blade can result in "skip lesions," have the potential for perforation, and lack precision and reproducibility when created manually. Use of a femtosecond laser avoids "skip lesions," minimizes the risk of perforation, increases precision and reproducibility, and allows better centration, angulation, and pairing of incisions. In addition, the fem- tosecond laser provides room for creativity, for instance allowing a sub-Bowman's ap- proach to AKs. However, the nomograms for femtosecond laser astigmatic keratom- etry are still being optimized. "The key thing is to pick the right patients who are good candidates, be they for toric lenses or AKs," said Dr. Trattler. Surgeons should evaluate both preop keratometry with devices such as the IOLMaster (Carl Zeiss Meditec, Jena, Germany) or Lenstar (Alcon), and preop topography, making sure that the test results are repeatable. "Confirm that the astigmatism aligns when multiple measurements are taken," he said. "Both magnitude of the astigma- tism and the axis should line up nicely." If there are significant disparities between readings, he added, surgeons should repeat testing and evaluate closely for dry eye or meibomian gland dysfunc- tion. Dry eye and a rapid tear film breakup time, he said, lead to irregularities in the measurement of corneal astigmatism, which can lead to inaccurate results. How do you determine whether a patient is best suited for an AK/LRI, toric lens, or a simple monofocal lens? Dr. Trattler illustrated the factors surgeons need to consider in a series of cases. Dr. Trattler's first case was that of a 63-year-old female with visually significant cataract, whose astigmatism went from relatively regular through the central visual axis to increasingly irregular in the periph- ery. The lobster claw pattern is consistent with a diagnosis of pellucid marginal degeneration. Because the astigmatism through the visual axis was very linear, not skewed, and regular, Dr. Trattler felt comfortable implanting a toric IOL. The patient achieved 20/20 at postop day five and was very pleased with the quality of vision. On the other hand, in a patient whose astigmatism was skewed, asymmetrical, or angulated, Dr. Trattler went with a monofocal. A monofocal lens was also Dr. Trattler's choice in a patient with kera- toconus. Although the astigmatism was relatively regular, there was asymmetry from top to bottom. The keratoconus also meant an unstable cornea that precluded the use of AKs or LRIs. In a final case (see images on next page), Dr. Trattler presented corneal topography with steepening and flattening "all over the map," illustrating a classic case of dry eye. In this case, Dr. Trattler spent time treating the patient with topical steroids and topical cyclosporine, improv- ing the topography over one month. If Dr. Trattler had gone with the initial measurements, he would have implanted an 18.5 D lens; after treatment, he found that the patient needed a 20.5 D lens. "This big shift in IOL power just by treating the dry eye is why it's so important to iden- tify dry eye, treat patients, and then test them one more time before you perform their surgery," he said. Ultimately, said Dr. Trattler, whether you use a toric IOL or an LRI, preop evaluation of topography and keratometry is critical for optimizing the management of 63-year-old female with visually significant cataract; astigmatism relatively regular through the central visual axis

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