Eyeworld

76 | EYEWORLD | MARCH 2021 R EFRACTIVE by Liz Hillman Editorial Co-Director About the physicians Maria Jose Cosentino, MD Instituto de la Vision University of Buenos Aires Buenos Aires, Argentina Evan Schoenberg, MD Georgia Eye Partners Atlanta, Georgia Relevant disclosures Cosentino: None Schoenberg: None C orneal ectasia after laser vision correction was first reported in 1998 by Theo Seiler, MD, PhD, 1 and since then, preop screening and treatment parameters have improved to help avoid such a complication. The incidence of post-LASIK ectasia (as it is commonly referred to though ectasia can occur with other refrac- tive and corneal procedures) is not officially known. Research from the early 2000s puts it at 0.2–0.6%. 2,3,4 A retrospective review in 2018 of 30,167 eyes that had LASIK (16,732 patients) from 2007–2015 with follow-up between 2 and 8 years saw an ectasia incidence of 0.033% over this timeframe. 5 "Over the 20+ years of experience since [the first LASIK cases], we've gained a lot of knowledge about both the corneal anatomy and the impact of LASIK on the cornea," said Evan Schoenberg, MD. "Unfortunately, some of that knowledge is from experience because some patients have developed ectasia. Along the way we've also developed better diagnostic devices. I think the playing field has changed a lot since the early days of LASIK, and it's a combination of better diagnostics and better awareness." Maria Jose Cosentino, MD, had a similar viewpoint on the reason for decreasing post-re- fractive surgery ectasia incidence. "Nowadays the incidence of corneal ectasia after LASIK is decreasing due to, on one hand, the existence of risk-calculation indices (the new and updated traditional ones) and on the other hand, the new alternatives for the refrac- tive treatment of moderate and high myopias that prevent the weakening of the cornea," she said. Dr. Schoenberg said he thinks the biggest change to further reducing ectasia risk has been awareness of the risk factors for corneal ectasia and the development of scoring systems for those risk factors. "I like the Randleman ectasia score. I don't think it says everything about the risk for ecta- sia, but it nicely summarizes some of the basic factors that we look at," he said, noting the variables of the Randleman score: topographic pattern, predicted residual stromal bed (RSB) thickness, age, preoperative corneal thickness (CT), and manifest refraction spherical equiv- alent (MRSE). "It's a useful summary of the basics you want to look at, but it's not the only thing you want to look at. "The addition of imaging systems like Pen- tacam [Oculus] and Galilei [Ziemer] that pro- vide information on the posterior cornea is the other widespread revolution in understanding high-risk patients for LASIK. More recently the addition of epithelial mapping has been another valuable tool," Dr. Schoenberg said, adding that he doesn't have much experience with epithelial mapping yet. "Another tool that I don't use rou- tinely but I have in my arsenal is genetic testing. … We tend to think that most patients who get post-LASIK ectasia after successful surgery are probably patients who would have had some degree of subclinical or clinical keratoconus anyway." Dr. Cosentino brought up irregular corneal topography as an important risk factor to watch out for. "Randleman et al. reported corneal topo- graphic irregularity in 50% of the patients with corneal ectasia," she said. 6 Candidacy for a refractive procedure is more than just preop testing. Dr. Schoenberg emphasized the safe ranges to which the cornea can be altered. Dr. Cosentino also mentioned the operative risk factors—a thin preoperative cornea and/or thick LASIK flap. "In moderate myopes I start talking about and in higher myopes I recommend an im- plantable collamer lens," Dr. Schoenberg said. "Rather than recommending a –9 LASIK, which is an on-label treatment, I would typically talk to that patient about an implantable collamer lens. That might be the shift in thinking that can change the [incidence of ectasia]." Dr. Cosentino also addressed percent tissue altered (PTA) as a factor to look at, with 40% PTA or higher being a risk factor for post-LASIK ectasia. "Marcony Santhiago, MD, proposed a metric for calculating the ectasia risk in patients who have undergone the LASIK procedure. 7 This metric can be expressed in terms of the following equation: PTA=(FT+AD)/CCT," Dr. Cosentino said. Technology, screening improvements decrease already low refractive surgery ectasia risk Contact Cosentino: majose.cosentino@icloud.com Schoenberg: evan.schoenberg@ gaeyepartners.com

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