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EW FEATURE 88 Laser vision correction • February 2018 axis. But 75% of the time, I'm on the topographic axis." Normalizing keratoconus or other irregular corneas "Topographic ablations are designed for abnormal corneas," said Karl Stonecipher, MD, Greensboro, North Carolina. "This topography- guided treatment to normalize the cornea has been combined with crosslinking to lock it into place. With topographic ablations, we are taking your God-given optical system and normalizing the topogra- phy to a reference shape. "Today, there is controversy about whether to use topogra- phy-guided refractive laser vision correction or topographic modified refraction laser vision correction," Dr. Stonecipher said. "Contoura [Alcon, Fort Worth, Texas] was orig- inally used to fix sphere and cylin- der, then we normalize topography. Now, we are normalizing the cornea with this topographic modified re- fraction and treating the sphere and cylinder. The question is, how do we treat keratoconus that is not forme fruste keratoconus? Should we do this topographic modified refraction and do laser vision correction? Or should we do what we're calling TCAT, or topographic treatments, to normalize the cornea and laser vision correction on top of that at the same time?" Post-refractive surgery patients According to Dr. Stonecipher, a wavefront-optimized patient with residual topographic abnormalities should be treated with TCAT. "If you have a patient who has undergone TCAT, and he or she has a perfectly normal cornea but residual refrac- tive error, you want to use wave- front-optimized," he said. Dr. Stonecipher and his daugh- ter recently published an article on the influences of enhancement with this laser system, and they evaluated 4,029 cases. The enhancement rate was 0.74%. "You're not enhancing many people because we are typical- ly getting them to 20/20," he said. "Now, we're trying to figure out how to give them better than normal vision. We're hoping to emulate what happened in the study, which is that approximately one-third of the patients got better vision than what they had before in their glasses or contact lenses." According to Dr. Gordon, in the United States, surgeons can only treat corneas that have a Q value of 0 to –1. "Most patients who have had previous myopic surgery have a Q value greater than 0, meaning it's on the plus side. In this case, you have to reduce the spherical aber- ration on the target to 0 in order to do it. It's like doing a hyperopic treatment," he said. "You have to do a C12 C4 neutralization. You have to look at how much myopia you're going to induce, just by trying to minimize the amount of positive spherical aberration." Dr. Krueger treats previously treated eyes on an off-label basis. "In those particular cases, I'm often likely to correct the aberrations and some of the astigmatism without necessarily getting it all, as far as astigmatism or myopia goes," he This patient is 1 year postop, –7.75 D in left eye (–7.0 D in right eye). Topo-guided patient is 20/15, 20/15, 20/15+2 OU. This is a pre- and postop higher order aberration map, seeing the improvement in Zernike values. Current continued from page 86 Monthly Pulse Laser vision correction EyeWorld Monthly Pulse is a reader survey on trends and patterns for the practicing ophthalmologist. Each month we send an online survey covering different topics so readers can see how they compare to our survey. If you would like to join the physicians who take a minute a month to share their views, please send us an email and we will add your name. Email carly@ eyeworld.org and put "EW Pulse" in the subject line. I would best describe my practice in the following way: For dry eye diagnosis we per- form tear film osmolarity testing to supplement exam findings We have a corneal topographer and use it to rule out keratoconus in preoperative refractive and/or cataract patients We have a wavefront analyzer to identify and measure higher order aberrations All of the above For patients considering refractive surgery, I find the following scenarios acceptable: For patients who have anterior basement membrane dystrophy (ABMD), PRK can treat both their refractive error and ABMD For patients with spherical corneas who have acceptable corneal thickness, both LASIK or SMILE are great options to consider PRK, LASIK, and SMILE all work well barring the potential of ectasia A and C A, B, and C

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