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I MANAGING IRREGUR CORNEAS PRIOR TO CATARACT SURGERY N FOCUS 42 | EYEWORLD | NOVEMBER 2019 tomography and suggested classifying corneas in Fuchs' patients as clinically definite edema based on a slit lamp exam, subclinical edema based on tomography, or no edema. "This classification is independent of [central corne- al thickness] and should be considered when evaluating [Fuchs' dystrophy] eyes for cataract surgery or EK," the study authors wrote. Winston Chamberlain, MD, said most of the irregular astigmatism in patients with Fuchs' is associated with advanced disease and stromal swelling. "Epithelium can become uneven and thickened with edema and basement membrane changes and can generate an irregular topogra- phy. If advanced enough, some patients develop scarring from microstructural changes in the stroma and recurrent bullae and microcysts," Dr. Chamberlain said. I n general, there is an underappreciation for the astigmatism associated with Fuchs' dystrophy, according to Kathryn Colby, MD, PhD. "There are some cases—the really sick corneas with blisters and things like that— where it's visually significant," Dr. Colby said, but a paper published in Ophthalmology determined that irregular astigmatism associated with Fuchs' might not be so obvious. 1 It could have implications if a Fuchs' patient needed cataract surgery. The paper by Sun et al. looked at loss of parallel isopachs, displacement of the thinnest part of the cornea, and focal posterior corneal surface depression, using tomographic pachym- etry and Scheimpflug images in 93 eyes that had a range of Fuchs' dystrophy severity. The study authors concluded that subclinical corneal edema could be identified with Scheimpflug Cataract surgery and addressing irregular astigmatism in Fuchs' Changes in corneal topography after DMEK. This patient had DMEK in both eyes. Both corneas had a change in the pattern of the axial map. Both corneas had a reduction in the total refractive power as measured by Scheimpflug photography with a net flattening (hyperopic shift), much greater in the left eye. The topographic astigmatism changed more in the left eye as well. This example demonstrates the challenges in predicting both conventional and toric IOLs before DMEK is done. Source: Winston Chamberlain, MD continued on page 44 by Liz Hillman EyeWorld Editorial Co-Director At a glance • How to handle IOL calculations and cataract surgery in a patient with Fuchs' dystrophy and irregular astigmatism varies by patient. • In some cases, a combined endothelial keratoplasty and phaco procedure can produce fair refractive outcomes. • In other cases, a staged procedure is needed with endothelial keratoplasty to regularize the cornea for accurate IOL power calculations. • In combined procedures, surgeons target the IOL powers with a hyperopic shift in mind. About the doctors Winston Chamberlain, MD Associate professor of ophthalmology Oregon Health Sciences University Portland, Oregon Kathryn Colby, MD, PhD Louis Block Professor and Chair, Department of Ophthalmology and Visual Science University of Chicago Medicine & Biological Sciences Chicago Mark Terry, MD Professor of ophthalmology Oregon Health Sciences University Portland, Oregon

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