Eyeworld

EW SECONDARY FEATURE 90 February 2018 by Vanessa Caceres EyeWorld Contributing Writer Testing for corneal dystrophies could pinpoint poor candidates for refractive surgery Dr. Hwang said. Refractive surgeons need to know how to explain the ra- tionale for the test in asymptomatic individuals, he thinks. Going forward, ophthalmol- ogists will need to become more aware of the role they will play in explaining any kind of genetic testing related to eye disease, Dr. Hwang said. This includes corneal dystrophies, age-related macular degeneration, glaucoma, and other conditions as availability of genetic testing for eye disorders increases. "You need to understand how the information and results, positive or negative, will affect the likelihood of developing disease in an indi- vidual and what that means for the patient," Dr. Hwang said. Even if genetic counselors are involved with explaining test results, ophthalmol- ogists will have a role as well. "Even if an ophthalmologist doesn't order the genetic test, he or she will be part of the patient discussion about interpretation, as well as implica- tions for management, follow-up, and prognosis," Dr. Hwang said. Ophthalmologists may find the American Academy of Ophthalmol- ogy's guidelines on genetic testing for inherited eye diseases, released in February 2014, to be helpful, 2 he added. Avellino Labs continues its work into other genetic tests, including a potential test for keratoconus, Mr. Korney said. EW References 1. Song Y, et al. Prevalence of transform- ing growth factor ß-induced gene corneal dystrophies in Chinese refractive surgery candidates. J Cataract Refract Surg. 2017 Dec 9. Epub ahead of print. 2. AAO Task Force on Genetic Testing. Recom- mendation for genetic testing of inherited eye diseases – 2014. www.aao.org/clinical-state- ment/recommendations-genetic-testing-of-in- herited-eye-d Editors' note: Dr. Hwang, Dr. Manche, and Mr. Korney have financial interests with Avellino Labs. Dr. Randleman has no financial interests related to his comments. Contact information Hwang: david.hwang@ucsf.edu Korney: scott@avellinolabs.com Manche: edward.manche@stanford.edu Randleman: randlema@usc.edu Commercial lab testing has expanded role in practices, especially among specific populations A s LASIK and other refrac- tive surgeries become safer, a growing number of refractive surgeons are trying to further reduce risk with genetic testing for corneal dystrophies. This includes testing for the most common corneal stromal dystrophies: granular corneal dys- trophy type 1 (GCD1), GCD2 (also called Avellino dystrophy), lattice, Reis-Bucklers, and Thiel-Behnke. If refractive surgery takes place in patients with one of these dys- trophies, such as Avellino/GCD2, it could have devastating visual results. "Patients with Avellino dystrophy who undergo LASIK surgery typical- ly develop dystrophic deposits at the level of the LASIK flap interface," said Edward Manche, MD, profes- sor of ophthalmology, and director of the cornea and refractive surgery service, Byers Eye Institute, Stanford University School of Medicine, Palo Alto, California. "Creation of the LASIK flap seems to accelerate the deposition of the dystrophic depos- its. These deposits tend to become visually significant and can lead to a significant decrease in corrected distance visual acuity." Even after multiple interven- tions, the deposits can recur; in some cases, penetrating keratoplasty is needed, said David G. Hwang, MD, FACS, professor, vice chair of ophthalmology, and director of cornea and refractive surgery ser- vices, Beckman Vision Center, UCSF School of Medicine, San Francisco. A test that has been available from the company Avellino Labs (Menlo Park, California) is used by eye surgeons who want to lower the chances that one of these dystro- phies may occur. The physician-or- dered test involves swabbing inside the patient's cheeks, said Scott Korney, COO of Avellino Labs. Each patient's test is given a unique ID number to ensure HIPAA compli- ance, and the test is sent in a special envelope to the company's lab in California. Processing typically takes 2 business days, although some tests are completed in 1 day, Mr. Korney said. Results are then sent to physicians via a password-protected, encrypted electronic web portal. The test has been qualified as 100% accurate, with no false posi- tives in clinical trials, according to the company's website. "A lot of clinics make decisions about proceeding or not proceeding with surgery based on the test," Mr. Korney said. The test is useful also because the subtle signs of these dystrophies can be misdiagnosed or missed com- pletely, Mr. Korney added. At oph- thalmology meetings, he has shown clinical images of the dystrophies without letting surgeons know what they were. Often, attendees misdi- agnosed what they saw and did not consider the possibility of corneal dystrophies. Who takes the test There are some patients best suited for the dystrophy test. "In younger patients with any corneal opacities, testing is like- ly warranted, as it is noninvasive and relatively inexpensive," said J. Bradley Randleman, MD, professor of ophthalmology, and director of cornea, external disease, and refrac- tive surgery, USC Roski Eye Institute, Keck Medicine of USC, Los Angeles. "Most of these tests will be negative, but it will provide an added level of comfort about their candidacy for refractive surgery." Patients with a family history of corneal dystrophies or corneal trans- plantation for an unknown etiology are potentially good candidates for the test, Dr. Manche said. "You need to have a high index of suspicion in patients of Japanese and Korean ancestry as these are the populations with the highest incidence of Avellino dystrophy," Dr. Manche said. The overall prevalence of corne- al dystrophies isn't well stated, but a recently published study among the Chinese population found an incidence of 1 per 416 people for the five most common corneal dystro- phies, 1 Mr. Korney said. Another published estimate for the preva- lence of Avellino corneal dystrophy in Korea has been 1 per 800 people, Dr. Hwang said. It's also crucial to perform a careful examination in patients in their 20s and 30s of Korean and Japanese ancestry as corneal opaci- ties can be subtle in this group, Dr. Manche said. Corneal dystrophies such as Avellino are thought to be much less common among other population groups, so the diagnostic yield of stromal corneal dystrophy testing in non-Asian refractive surgery candi- dates may be lower, Dr. Hwang said. "We should soon have data on the prevalence of Avellino and other corneal stromal dystrophies in pop- ulations of predominantly European descent. It's probably lower by a factor of 2 or 3," he said. Formal guidelines regarding when to perform this kind of ge- netic testing are not yet created, Dr. Hwang said. Still, "When in doubt, testing is reasonable," Dr. Randleman said. "The turnaround time is generally 2 to 3 days, and both the surgeon and patient will be happy knowing that there is no problem before surgery." An expanding role for genetic testing With the growing use of genetic testing among the general public, the idea of testing for these dystro- phies is widely accepted, Mr. Korney said. "General public awareness [of DNA testing] is good for the whole industry," Mr. Korney said. The test from Avellino Labs will have a CPT reimbursement code as confirmation testing (but not as a screening test) beginning on Aug. 31, he added. The higher incidence of both myopia and transforming growth factor beta-induced (TGFBI) corneal dystrophies among certain pop- ulations makes the testing more common in some parts of the world, but does not exclude the need for testing for this condition found in all regions of the world; in parts of Asia, up to 80% of people hav- ing refractive surgery will take the commercial lab test first, Mr. Korney said. Patients also tend to respond well to the idea of eliminating risk in case someone has Avellino or another one of the dystrophies. The results from the Avellino Labs test may be straightforward to explain, but not all DNA tests are,

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