EyeWorld India March 2020 Issue

CORNEA EWAP MARCH 2020 43 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 pachymetry 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 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 corneal 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 topography. If advanced enough, some patients develop scarring from microstructural changes in the stroma and recurrent bullae and microcysts,” Dr. Chamberlain said. When Fuchs patients need cataract surgery, deciding whether to do a combined procedure (if a corneal procedure is needed) or staged procedure depends on the patient. And if it’s combined, how does the physician determine IOL power? Mark Terry, MD, described a recent case where a patient with Fuchs put off cataract and transplant surgery. The patient had massive corneal swelling, blistering, and scarring on the surface. The patient’s other eye also had Fuchs, though less severe, and its axial length was the same as the other eye. Dr. Terry asked the patient how his vision was 10–20 years prior, finding out that the patient could see well without glasses in both eyes. As such, Dr. Terry planned an IOL based on the patient’s healthier eye and performed a triple procedure where he removed the scar, performed phaco, and followed with DMEK. “I took the keratometry on the eye that did not have swelling and used that for my calculations on the eye that had terrible swelling, that way I could feel confident that the IOL I put in would have the same outcome as if he didn’t have the horrible swelling,” Dr. Terry said. But what if the patient hadn’t seen well without glasses prior? What if the axial lengths were different? In cases where you can’t obtain accurate keratometry in the face of known irregular astigmatism, Cataract surgery and addressing irregular astigmatism in Fuchs 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. Contact information Chamberlain: chamberw@ohsu.edu Colby: kcolby@bsd.uchicago.edu Terry: MTerry@deverseye.org 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 This article originally appeared in the November 2019 issue of EyeWorld . It has been slightly modified and appears here with permission from the ASCRS Ophthalmic Services Corp.