Eyeworld

EW CORNEA 38 June 2015 by Lauren Lipuma EyeWorld Staff Writer A new genetic test, the first of its kind, can identify patients who are at risk for developing sight-threating complications after refractive surgery I t is rare for a single-gene test to offer immediate benefits to both the patient and the physician, but that is exactly the case with the Avellino DNA Test for LASIK Safety (Avellino Lab USA, Menlo Park, Calif.). The Avellino DNA Test is a simple, rapid, affordable test that can identify patients who possess mutations that lead to granular cor- neal dystrophy (GCD) types I and II. GCD causes opacities to build up in the corneal stroma, and undergoing LASIK or other refractive procedures can exacerbate these symptoms, leading to vision loss treatable only by deep anterior or penetrating kera- toplasty. The first test of its kind, the Avellino test has screened nearly a half million patients for GCD so far, uncovering more than 450 positive results. Screening patients preoperative- ly with the Avellino DNA Test adds a level of safety to refractive proce- dures—patients with these muta- tions can opt out of surgery before it's too late, eliminating the risk of potentially devastating vision loss from GCD. Incorporating the Avellino DNA Test into a practice also gives sur- geons a precise advantage in a tough refractive market. Arming patients with their test results, physicians can ease some of the patient fears about LASIK, inspire confidence in the procedure, and boost their refractive surgery volume. The benefit to the patient Mutations in the transforming growth factor, beta-induced (TGFBI) gene lead to 5 autosomal dominant corneal dystrophies—GCD type I, GCD type II (also called Avellino corneal dystrophy), Reis-Bücklers corneal dystrophy, Thiel-Behnke cor- neal dystrophy, and lattice corneal dystrophy type I. These mutations cause deposits of abnormally folded keratoepithelin proteins to build up in either the corneal stroma or Bow- man's layer, creating opacities that can lead to significant vision loss. Homozygous individuals become visually impaired in ado- lescence and early adulthood, but heterozygous individuals experience milder disease, with visual impair- ment occurring late in life. But if heterozygotes experience corneal damage—say from trauma or refrac- tive surgery—the natural wound healing response triggers expression of the TGFBI protein. Opacities then build up at the site of the wound; after LASIK, they cover the entire area of the flap. This can happen at almost any time postoperatively, from months to years after surgery. Many corneal dystrophies are contraindications for LASIK, but het- erozygous patients could decide to have refractive surgery before clin- ical symptoms appear. Even when the opacities are visible at the preop exam, they can easily be mistaken for something else, such as corneal scarring associated with previous corneal injury or infection. "Doctors miss that the eye would be a risk, when those spots could be early signs of corneal dystrophy," said Scott Korney, chief operating officer of Avellino Lab. "Doctors just aren't thinking that way—they're not looking for corneal dystrophy because they see it as a fairly uncommon condition." GCD has fallen off refractive surgeons' radar, but they should start paying greater attention to it, said Mitchell Jackson, MD, in pri- vate practice, Lake Villa, Ill. Recent research suggests that the global heterozygous prevalence of GCD is greater than initially thought. It could even be more prevalent than keratoconus—the biggest preop con- cern to a refractive surgeon. Even if the risk of these com- plications is low, physicians have a responsibility to patients to make the procedure as safe as possible, Dr. Jackson said. "Our job is to deliv- er the best outcomes, but also to reduce risk." The benefit to the surgeon LASIK volume has dropped in recent years, despite an enlarging pool The DNA test that can boost a refractive practice A 37-year-old patient who had LASIK when she was 24 (13 years ago). She has limited vision with GCD progressing quickly. The patient is currently being evaluated for a corneal transplant, with the knowledge the condition will return. Early signs of GCD are so subtle that they are often overlooked on a slit lamp exam or mistaken for something else. Source: Scott Korney continued on page 40

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