Eyeworld

116 | EYEWORLD | APRIL 2019 C ORNEA by Maxine Lipner EyeWorld Senior Contributing Writer RESEARCH HIGHLIGHT Contact information Parker: Jack.parker@gmail.com Double trouble With this in mind, practitioners are often leery of eyes that have had prior RK. "Having a cornea that is beset by RK doesn't mean you can't have additional problems and that includes endothelial decompensation," Dr. Parker said. The endo- thelium may go bad as a result of RK incisions that were too deep or if too many incisions were used, but sometimes the decompensation is from an entirely different issue like Fuchs' dystrophy. "Sometimes patients are doubly unlucky and they have RK and Fuchs' dystrophy," Dr. Parker said. The issue becomes what to do for these individu- als to preserve their vision. "You would like to be as minimally invasive as possible and you would like to try to restore the anatomy of the cornea back to as normal as possible without doing any- thing extra," he said. Investigators found themselves with such a population in the clinic; patients had issues from previous RK as well as Fuchs' dystrophy. They sought to simply replace the endothelium using DMEK, with the idea of doing as minimal surgery as they could for these patients. "With DMEK, the trick is once you put the cells into the eye, you want it to stick to the back of the cornea," Dr. Parker said. "The question was whether these incisions in the cornea made by the RK were going to interfere with the process of unfolding the cells in the eye or the action of sticking those cells to the back of the cornea where they belong." Fixing corneal shape The study assessed outcomes in these cases. "Dogma with DMEK is that when you replace the back of the cornea, the shape of the cornea doesn't change," Dr. Parker said. "When you replace just the back 5% of the cornea, you don't expect the front 95% to have very much of a change of shape." Prior to surgery, investigators observed that not only did patients have scars from their RK incisions, but the corneas had lost most of their structural support. "They're drooping, sagging, or twisted in all sorts of undesirable ways," Dr. D espite the small amount of cornea be- ing replaced in Descemet's membrane endothelial keratoplasty (DMEK), the procedure can offer surprisingly positive outcomes for Fuchs' dystro- phy patients who previously under- went radial keratotomy, according to Jack Parker, MD, PhD. Even for patients who had extremely irregularly shaped corneas, as in a study 1 published in Cornea, DMEK alone was able to normalize the shape and offer excellent acuity, Dr. Parker said. Included in the study were five eyes of three Fuchs' dystrophy patients who had undergone previous radial keratotomy (RK). Since then, the center has performed DMEK on five additional RK eyes with Fuchs' dystrophy. One of the issues with eyes that have undergone RK is that they have notoriously unstable corneas, Dr. Parker explained, adding that because these incisions are made in the cornea and often extend out to the limbus, they can be difficult to get around. In ad- dition, they're frequently quite numerous and can present a problem for any kind of surgical manip- ulation the surgeon is going to do in the eye. DMEK after radial keratotomy An eye with RK immediately after DMEK Source: Jack Parker, MD, PhD continued on page 118 About the doctor Jack Parker, MD, PhD Parker Cornea Birmingham, Alabama Reference 1. Parker JS, et al. Clinical out- comes of Descemet membrane endothelial keratoplasty in eyes with previous radial keratotomy. Cornea. 2018;37:1351–1354. Financial interests Parker: None

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